improved parser / lexer:

- NEVER DIRECTLY throw an Error object on lexer or parser fail, but instead invoke the parseError() function and let it handle the situation. The lexer parseError() handler can return a lexer token ID (which always are truthy return values) or undefined/false, which makes the lexer produce an EOF token ID by default.

- when an parser error is non-recoverable, the return value of parseError() is returned as the RESULT of the parse itself (rather than some uncertain current $$ value)
Merge branch 'master' of github.com:GerHobbelt/jison

Conflicts:
	lib/jison.js
	web/content/assets/js/jison.js