#6 Improve token regexp towards JavaScript's full RegExp syntax

[Olivier Mengué]

JS/CC should use the same regexp syntax as JavaScript ast this is what the user is familiar with.
In particular:
- '\xxx' support should be dropped as it is ambiguous and is not in JavaScript
- '\uXX' and '\UXXXX' should be added for full Unicode support
- '.' should have the same effect (not match end of line)