The ANTLRv4 grammar is now equivalent to the ANTLRv3 grammar (#4424)

* The grammar is now equivalent to the ANTLRv3 grammar

- The LexBasic.g4 grammar has been removed and the few used rules have been taken over into ANTLRv4Lexer.g4. This lowers complexity and increases readability of error messages (e.g. missing ';' instead of missing SEMI).
- The wrong definition of element options for action (and sempred) blocks has been fixed.
- A predefined token file is now part of the set to make sure tokens appear in the right order (for tree walkers that were ported from ANTLRv3).

This grammar is now used in antlr-ng for generating parser, so it should also appear as the official grammar (since the one in ANTLRv4 is actually a v3 grammar).

* Also update the local copies of the ANTLRv4 lexer grammar.

* Missed some changes.

* Added required tokens file.

Author: mike-lischke