- Update after IFunction interfaces changes
- move type checks into FunctionCountMatches::getReturnTypeImpl()
- Use StringRef over String
- Separate out logic for counting sub matches into separate helper
- Do not copy other regular expression matches, only the first
- Add some comments
- Set is_no_capture, to avoid check for number of subpatterns
- Add countMatchesCaseInsensitive()
- Reguster functions in case-sensitive manner, since this is not SQL
standard
