* include/std/functional (_Unwrap): Rename to __inv_unwrap.
	(__invfwd): Adjust.
	(__invoke_impl): Remove unused template parameters.
	* testsuite/20_util/function_objects/invoke/59768.cc: Remove unused
	parameter.
	* testsuite/20_util/function_objects/invoke/ref_ext.cc: Copy 59768.cc
	and test __invoke extension for C++11.

From-SVN: r239120