Add total duration column to stats

[milianw]

Implements #67

Example output for io:

Syscalls latency statistics (usec):
Type                    Count            Min        Average            Max          Stdev          Total
--------------------------------------------------------------------------------------------------------
Open                      730          3.072         19.220       1308.384         69.425      14030.816
Read                      173          0.768        383.774       8908.736        917.306      66392.832
Write                     130          0.992          8.207         72.960          7.149       1066.880
Sync                        0          0.000          0.000          0.000              ?          0.000

Disk latency statistics (usec):
Name                    Count            Min        Average            Max          Stdev          Total
--------------------------------------------------------------------------------------------------------
sda                         1        163.264        163.264        163.264              ?        163.264

For syscalls:

Per-TID syscalls statistics (usec)
sh (2964, TID: 2964)                            Count            Min        Average          Max      Stdev          Total  Return values 
 - openat                                         576          3.168         22.459     1615.712    104.527       12936.48  {'success': 172, 'ENOENT': 406}
 - mmap                                           292           2.24          8.742        81.12       6.24       2552.768  {'success': 293}
 - ioctl                                          239          0.576        296.328    62666.752   4052.624      70822.464  {'success': 239, 'ENOTTY': 2}
 - newfstat                                       165          0.512          1.339        3.424      0.486        220.864  {'success': 166}
 - read                                           161            0.8        474.111     20462.88   2066.455      76331.808  {'success': 162}
 - close                                          161          0.576          1.257        3.232      0.465          202.4  {'success': 162}
 - newfstatat                                     140          2.752         81.307     5750.816    519.782       11383.04  {'success': 125, 'ENOENT': 17}
 - mprotect                                        87          3.968          9.173       26.816      3.111        798.016  {'success': 88}
 - munmap                                          77           5.12         11.322       34.272      4.666        871.776  {'success': 78}
 - write                                           45          1.184          6.599       16.512      3.625         296.96  {'success': 46}
 - sched_yield                                     43          1.856         15.195       79.232      27.13        653.376  {'success': 44}
 - readlinkat                                      24          6.432         14.176       23.456      4.803        340.224  {'success': 17, 'EINVAL': 9}
 - rt_sigprocmask                                  22          0.544          1.129        2.688      0.732         24.832  {'success': 23}
 - fcntl                                           20           1.28          1.704        2.272      0.305          34.08  {'success': 21}
 - futex                                           19          0.864       2897.145    35267.488   8229.159       55045.76  {'success': 20}
 - brk                                             18           1.28          5.205        12.96      2.512         93.696  {'success': 19}
 - faccessat                                       14          4.864          9.088        20.32      4.985        127.232  {'success': 6, 'ENOENT': 10}
 - rt_sigaction                                    12           0.64          1.299        2.944      0.738         15.584  {'success': 13}
 - getdents64                                      12          0.928        171.123      1002.08    357.085       2053.472  {'success': 13}
 - geteuid                                          8          0.384          0.804         1.44      0.388          6.432  {'success': 9}
 - getuid                                           8          0.352          0.792        1.376      0.331          6.336  {'success': 9}
 - getgid                                           6           0.32          0.528        0.672      0.126          3.168  {'success': 7}
 - clock_gettime                                    6          0.512          1.488        2.112      0.745          8.928  {'success': 7}
 - clone                                            6         19.264         28.453       33.344      5.235         170.72  {'success': 7}
 - getegid                                          6           0.32          0.677        1.024      0.284          4.064  {'success': 7}
 - epoll_ctl                                        5          3.904          4.339        4.992      0.475         21.696  {'success': 6}
 - newuname                                         3            0.8          2.069        2.784      1.102          6.208  {'success': 4}
 - statfs                                           3          7.168          7.765         8.32      0.577         23.296  {'success': 4}
 - getrlimit                                        3            1.6           1.76         2.08      0.277           5.28  {'success': 4}
 - eventfd2                                         2          6.304          8.176       10.048          ?         16.352  {'success': 3}
 - sched_getaffinity                                2          1.824          2.256        2.688          ?          4.512  {'success': 3}
 - setsockopt                                       2          1.248         12.656       24.064          ?         25.312  {'success': 3}
 - set_tid_address                                  1           1.92           1.92         1.92          ?           1.92  {'success': 2}
 - clock_getres                                     1          2.144          2.144        2.144          ?          2.144  {'success': 2}
 - set_robust_list                                  1          1.216          1.216        1.216          ?          1.216  {'success': 2}
 - getpid                                           1          1.408          1.408        1.408          ?          1.408  {'success': 2}
 - bind                                             1          7.232          7.232        7.232          ?          7.232  {'success': 2}
 - execve                                           1       3874.912       3874.912     3874.912          ?       3874.912  {'success': 2}
 - getsockname                                      1          1.376          1.376        1.376          ?          1.376  {'success': 2}
 - nanosleep                                        1        318.016        318.016      318.016          ?        318.016  {'success': 2}
 - socket                                           1         12.992         12.992       12.992          ?         12.992  {'success': 2}
 - lseek                                            1          1.888          1.888        1.888          ?          1.888  {'success': 2}
 - epoll_create1                                    1          6.912          6.912        6.912          ?          6.912  {'success': 2}
 - socketpair                                       1          23.84          23.84        23.84          ?          23.84  {'success': 2}
 - epoll_pwait                                      1          3.616          3.616        3.616          ?          3.616  {'success': 2}
 - timerfd_create                                   1          5.824          5.824        5.824          ?          5.824  {'success': 2}
Total:                                           2201                                                           239370.432                
-----------------------------------------------------------------------------------------------------------------

Total syscalls: 2201

Total duration: 239370.432000

[jdesfossez]

Looks good, just for the "Per-TID syscalls statistics" table, it should be right aligned like the other fields.