Improve AsciiChar compatibility with u8 and char
Improve AsciiChar compatibility with u8 and char

* Change is_whitespace() to also return true for AsciiCHar::VT and ::FF.
* Rename a bunch of ctype methods and make them take self by reference:
  * is_digit() => is_ascii_digit()
  * is_hex() => is_ascii_hexdigit()
  + is_control() => is_ascii_control()
  + is_graphic() => is_ascii_graphic()
  + is_blank() => is_ascii_blank()
  + is_print() => is_ascii_printable()
  * is_punctuation() => is_ascii_punctuation()
* Ddd identical _ascii methods when char also has methods without _ascii,
  except that the _ascii methods take self by reference:
  * is_ascii_alphabetic() = is_alphabetic()
  * is_ascii_alphanumeric() = is_alphanumeric()
  * is_ascii_uppercase() = is_uppercase()
  * is_ascii_lowercase() = is_lowercase()
* Add is_digit() which takes base as parameter.
* Add is_ascii_whitespace() which returns true for FF but not VT.

tomprogrammer/rust-ascii