RUBY-698 Support optional Regex compilation with pure Ruby de/serialization
RUBY-698 getmores need to pass down compile_regex option as well
RUBY-698 Support optional Regex compilation in c ext de/serialization
RUBY-698 separate flag logic in serialization for each regexp type
RUBY-698 Refactoring, separating flag definitions for bson and core regex, name change
RUBY-698 minor variable name change in c ext
RUBY-698 Only warn in documentation for #from_native and #try_compile
RUBY-698 Use more standard bit flag definition
RUBY-698 always add the m flag when converting from native to bson regex