Add 3 warnings and fix some message descriptions

+ Add some missing warnings seen in the wild: -Wdocumentation, -Wvla-
extension and -Wnested-anon-types (anonymous-union) .
* Complete description for Wweak-vtables (warn-weak-vtables) in semantic
file
* Fix missing operands descriptions in parse file
- Remove extra quotes in lex file
Merge pull request #4 from filippsen/gh-pages

Add 3 warnings and fix some message descriptions