re.c: use name_to_backref_number
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57110 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
re.c: use name_to_backref_number
casts.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57110 b2dd03c8-39d4-4d8f-98ff-823fe69b080e