parse.y: escape all closing parens

* parse.y (simple_re_meta): escape all closing characters, not only
  round parenthesis.  [ruby-core:53578] [Bug #8133]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39858 b2dd03c8-39d4-4d8f-98ff-823fe69b080e