Implement LC_NOTE

[woodruffw]

I'll probably do this tomorrow, but just to keep track:

struct note_command {
       uint32_t cmd;        // LC_NOTE
       uint32_t cmdsize;    // sizeof(struct note_command)
       char data_owner[16]; // owner name for this LC_NOTE
       uint64_t offset;     // file offset of this data
       uint64_t size;       // length of data region
};