vm.c: check cbase

* vm.c (rb_vm_cref_in_context): check also cbase, not only self.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44385 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
test_fileutils.rb: enclose helper methods

* test/fileutils/test_fileutils.rb: enclose helper methods in a
  module from global functions.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44386 b2dd03c8-39d4-4d8f-98ff-823fe69b080e