Bugfix: f_utf_is_whitespace_modifier() is incomplete.

Bugfix: f_utf_is_whitespace_modifier() is incomplete.

Remove "@see iscntrl()" which appears all over the place, incorrectly.
Make sure appropriate "@see" uses exist.

Remove unnecessary "== F_true" tests.

Implement is_punctuation and is_symbol discovery for ASCII characters.

Some function declarations are missing.
Some function implementations are missing.
Remove duplicate declaration of f_utf_character_is_word().

There are no whitespace modifiers in ASCII to my knowledge, and isdigit() is clearly from a copy and paste that was never completed.

Add notes about phonetic whitespaces and improve handling.