Progress: Continue string and convert changes, fixing bugs.

Progress: Continue string and convert changes, fixing bugs.

Document that the conversion operations are not ideal performance-wise.
Switch from fputc() to fwrite_unlocked() for the conversion print functions.
Use more bitwise operations rather than comparisons.
Explicitly handle binary print mode as it is easy to optimize.
(The binary optimization still uses much of the existing strategy and so likely can still be further optimized.)

Use correct digits for binary print in byte_dump.

Update the API documentation as it has fallen behind.
Preemptively update some of the API documentation where fputc/fputc_unlocked has not yet been fully updated to fwrite_unlocked.