re PR c++/79664 (ICE with #pragma omp parallel in constexpr function)

re PR c++/79664 (ICE with #pragma omp parallel in constexpr function)

	PR c++/79664
	* parser.c (cp_parser_omp_teams, cp_parser_omp_target): Use
	SET_EXPR_LOCATION on OMP_TARGET/OMP_TEAMS tree.
	* constexpr.c (potential_constant_expression_1): Handle
	OMP_*, OACC_* and CILK_* trees.  Use error_at with
	EXPR_LOC_OR_LOC (t, input_location) computed early
	instead of error, or error_at with location_of (t).

	* g++.dg/gomp/teams-1.C: Adjust expected diagnostic location.
	* g++.dg/cpp1y/constexpr-throw.C: Likewise.
	* g++.dg/gomp/pr79664.C: New test.

From-SVN: r245662