parse.y: label cannot be followed by a modifier

* parse.y (parse_ident): just after a label, new expression should
  start, cannot be a modifier.  [ruby-core:65211] [Bug #10279]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47696 b2dd03c8-39d4-4d8f-98ff-823fe69b080e