[PR72741] Properly handle clauses specifying the level of parallelism for 'external' Fortran OpenACC routines

..., so as to also for these enable the generic middle end OMP code to verify
proper nesting of loops/routines regarding their levels of parallelism.

	gcc/fortran/
	PR fortran/72741
	* openmp.c (gfc_match_oacc_routine): Set the level of parallelism
	for all variants.
	(gfc_resolve_oacc_routines): Call gfc_add_omp_declare_target.
	gcc/testsuite/
	PR fortran/72741
	* c-c++-common/goacc/routine-3-extern.c: New file.
	* c-c++-common/goacc/routine-3.c: Adjust.
	* c-c++-common/goacc/routine-4-extern.c: New file.
	* c-c++-common/goacc/routine-4.c: Adjust.
	* gfortran.dg/goacc/routine-module-3.f90: New file.
	* gfortran.dg/goacc/routine-external-level-of-parallelism-1.f: New
	file.
	* gfortran.dg/goacc/routine-external-level-of-parallelism-2.f:
	Likewise.

Co-Authored-By: Cesar Philippidis <cesar@codesourcery.com>

From-SVN: r269858