Introduce libgomp/testsuite/libgomp.c-c++-common

Introduce libgomp/testsuite/libgomp.c-c++-common

2017-09-14  Tom de Vries  <tom@codesourcery.com>

	* testsuite/libgomp.c++/cancel-taskgroup-1.C: Remove.
	* testsuite/libgomp.c/cancel-taskgroup-1.c: Move to ...
	* testsuite/libgomp.c-c++-common/cancel-taskgroup-1.c: ... here.
	* testsuite/libgomp.c/c.exp: Include test-cases from
	libgomp.c-c++-common.
	* testsuite/libgomp.c++/c++.exp: Same.  Force c++-mode compilation of .c
	files.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@252775 138bc75d-0d04-0410-961f-82ee72b054a4