Fix matching of case-instensitive literals
Fix matching of case-instensitive literals

Code that calculated which part of the input to match against a literal
was wrong in case of case-insensitive literals when generating
speed-optimized parsers. As a result, matching of case-insensitive
literals worked only at the end of the input (where too big length
passed to the |substr| method didn't matter).

Fixes GH-153.

Mingun/pegjs,mcanthony/pegjs,crguezl/pegjs,pegjs/pegjs,pegjs/pegjs,GerHobbelt/pegjs,wwall/pegjs-fn,jlturner/pegjs,Mingun/pegjs,Sciumo/pegjs,luisvt/pegjs,GerHobbelt/pegjs,mcanthony/pegjs,luisvt/pegjs,Sciumo/pegjs,crguezl/pegjs,wwall/pegjs-fn,jlturner/pegjs