* io.c (io_getpartial): remove unused kwarg from template

	* test/ruby/test_io.rb (test_readpartial_bad_args): new
	  [Bug #11885]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54352 b2dd03c8-39d4-4d8f-98ff-823fe69b080e