base and radix in numeric representation

[shirok]

There's some confusion in use of these terms.

In <write-controls>, we use radix as the explicit radix prefix, and base as the base of the actual number. However, R7RS uses radix as the base.　C API's argument and field names has similar confusion.

We may rename radix in <write-controls> as radix-prefix, which has little room of confusion. We want to use base consistently for N of base-N number notation, but we have to recognize R7RS uses radix for that.

[shirok]

Now I remember. Nomenclature of base and radix came from Common Lisp.