Update: implement utf strings, ensure endianess, and add isgraph()/isspace() methods...

Update: implement utf strings, ensure endianess, and add isgraph()/isspace() methods to UTF-8 equivalents

Expand the UTF-8 character type (a 4-byte wide character represented as a big-endian 32-bit integer) into working like f_string and f_dynamic_string.
Provide all similar functionality.

I have decided that the isgraph(), isspace(), etc.. functions fo UTF-8 should also call the ASCII equivalents.
Update all relating code.

Use memcmp() and memcpy() for comparing UTF-8 characters class (4-byte integer) to the UTF-8 char strings (multiple 1-byte char).
When doing this, make sure to do so with the proper endianess.

Add missing f_utf_character_to_char() function.

Wrap some of the macros parameters in parenthesis for safety reasons.

Add f_utf_is_big_endian() and document its use.

Provide custom EOL, EOS, and placeholder defines for UTF characters (4-byte integers).