Don't create location wrapper nodes within OpenACC clauses

This fixes a GCC 11, 10, 9 regression introduced by commit
dfd7fdca (Subversion r267272) "C++: more
location wrapper nodes (PR c++/43064, PR c++/43486)".  But: this isn't
intending to blame David, because back then, the problem hasn't been visible in
the testsuite (or else I'm sure would've been addressed right away) because of
our all dear friend: missing testsuite coverage.  Thus, for GCC 8, I'm likewise
enhancing the testsuite, without the C++ front end code changes.

I actually had presumed that there may be an issue for OpenACC:
<http://mid.mail-archive.com/874lb9qr2u.fsf@euler.schwinge.homeip.net

>, so here
we are, two years (and many "wasted" hours...) later...

	gcc/cp/
	* parser.c (cp_parser_omp_var_list_no_open): Assert that array
	section's 'low_bound', 'length' are not location wrapper nodes.
	(cp_parser_oacc_all_clauses, cp_parser_oacc_cache): Instantiate
	'auto_suppress_location_wrappers'.
	gcc/testsuite/
	* c-c++-common/goacc/cache-3-1.c: New.
	* c-c++-common/goacc/cache-3-2.c: Likewise.
	* c-c++-common/goacc/data-clause-1.c: Likewise.
	* c-c++-common/goacc/data-clause-2.c: Likewise.
	* c-c++-common/gomp/map-1.c: Adjust.
	* c-c++-common/gomp/map-2.c: Likewise.
	* g++.dg/goacc/cache-3-1.C: New.
	* g++.dg/goacc/cache-3-2.C: Likewise.
	* g++.dg/goacc/data-clause-1.C: Likewise.
	* g++.dg/goacc/data-clause-2.C: Likewise.
	* g++.dg/gomp/map-1.C: Adjust.
	* g++.dg/gomp/map-2.C: Likewise.

Reported-by: Sandra Loosemore <sandra@codesourcery.com>