Reduce duplicates in SmartCaseMatcher implementation
Reduce duplicates in SmartCaseMatcher implementation

by improving RegexpMatcher's API.  Now it has a function to get a flag
for regexp instead of a flag itself.

polamjag/peco,reiki4040/peco,peco/peco,dav009/peco,ken-saka/peco,ukitazume/peco