* eval.c (Init_eval): enable Refinements by default.
  [ruby-core:51286] [Bug #7667]

* eval.c (rb_mod_refine, top_using): show a warning when
  Module#refine or main.using is called at the first time.

* ext/refinement/*: removed the extension library "refinement".

* test/ruby/test_refinement.rb: fix for the above changes.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38729 b2dd03c8-39d4-4d8f-98ff-823fe69b080e