Don't use single byte optimization on grapheme clusters
Unicode Text Segmentation considers CRLF as a character. [Bug #15337]
add tests using Unicode test data for grapheme clusters
Add file test/ruby/enc/test_grapheme_breaks.rb to test String#each_grapheme_cluster
and \X extended grapheme cluster matcher in regular expressions against test data
provided by Unicode (ucd/auxiliary/GraphemeBreakTest.txt).
Some lines in the data file are ignored, as follows:
- Lines with a surrogate, because Ruby doesn't handle these
- The case of "\r\n", because there is a bug (#15337) in the implementation
remove guard against bug #15337, because it is fixed
merge revision(s) 65954,65955,65958: [Backport #15337]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@66073 b2dd03c8-39d4-4d8f-98ff-823fe69b080e