case insensitive match not working

[mschoch]

First reported to me by @aviadl, it appears that case-insensitive matching was not working.

We should be able to write regexes like (?i)marty and match marty, MARTY and mArTy among others.

When I first reviewed the code (and the rust version it was based on) it appeared that this was intended to work. See: https://github.com/couchbase/vellum/blob/master/regexp/compile.go#L71

But, looking at the impl it was clearly wrong. It detected that we wanted case-insensitive match, but proceeded to build a state machine with the single case. The rust version called a separate case_fold method on the character class, which added the other cases. Ours didn't have that method, and also seemed not be correctly ranging over all runes when case-insensitive was requested.

I have a potential fix coming, once I remember how gerrit works.

[mschoch]

Code review here: http://review.couchbase.org/#/c/110383/

[mschoch]

Closing this as the fix was merged a while back.