vm_method.c: alias warning at refined method

	* vm_method.c (rb_method_entry_make): suppress a warning at
	  refined method which will not be redefined.
	  [ruby-core:82385] [Bug #13817]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@59819 b2dd03c8-39d4-4d8f-98ff-823fe69b080e