Move forbid missing_doc to warning
Remove excess inline directives; Add methods for recognizing encoding chars

- Methods with long body would be inlined, which would ruin performance
- Add methods is_encoding_start_char and is_encoding_char to recognize
  encoding chars

Signed-off-by: DanielFath <daniel.fath7@gmail.com>
Remove PERef and EntityRef tokens; Add Amp,Percent and Semicolon tokens

- Removed PERef and EntityRef to simplify lexer and allow greater mixing
  of content in textual tokens. This way if a text has `&` or `%` it will
  allow for lexer to continue running without state, while the parser will
  have to deal with piecing together references
Add token EqTok for symbol `=`

- Add definition, parsing and tests for it
Add parsing for NMtoken
Merge branch 'break_ref'