* regparse.c (add_ctype_to_cc): don't check dup warn on adding
  negative ctype to cclass. [Bug #7471] [ruby-core:50344]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38805 b2dd03c8-39d4-4d8f-98ff-823fe69b080e