omp-low.c (check_omp_nesting_restrictions): Allow cancel or cancellation point with taskgroup clause inside of taskloop.

	* omp-low.c (check_omp_nesting_restrictions): Allow cancel or
	cancellation point with taskgroup clause inside of taskloop.  Consider
	a taskloop construct without nogroup clause as implicit taskgroup for
	diagnostics if cancel/cancellation point with taskgroup clause is
	closely nested inside of taskgroup region.

	* c-c++-common/gomp/cancel-1.c (f2): Add various taskloop related
	tests.

	* testsuite/libgomp.c-c++-common/cancel-taskgroup-4.c: New test.

From-SVN: r266722