In the function onigenc_unicode_case_map() in enc/unicode.c, deal
with the case that the ONIGENC_CASE_IS_TITLECASE flag is set on
lowercase characters. This is in preparation for Georgian Mtavruli,
which are uppercase but not titlecase, in Unicode 11.0.0.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65971 b2dd03c8-39d4-4d8f-98ff-823fe69b080e