Fix std::midpoint(T*, T*) for reversed arguments

	* include/std/numeric (midpoint(T*, T*)): Fix incorrect result.
	* testsuite/26_numerics/midpoint/pointer.cc: Change "compile" test
	to "run".

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@271606 138bc75d-0d04-0410-961f-82ee72b054a4
3 files changed