[PR92840] [OpenACC] Refuse 'acc_unmap_data' unless mapped by 'acc_map_data'

	libgomp/
	PR libgomp/92840
	* oacc-mem.c (acc_map_data): Clarify reference counting behavior.
	(acc_unmap_data): Add error case for 'REFCOUNT_INFINITY'.
	* testsuite/libgomp.oacc-c-c++-common/acc_unmap_data-pr92840-1.c:
	New file.
	* testsuite/libgomp.oacc-c-c++-common/acc_unmap_data-pr92840-2.c:
	Likewise.
	* testsuite/libgomp.oacc-c-c++-common/acc_unmap_data-pr92840-3.c:
	Likewise.
	* testsuite/libgomp.oacc-c-c++-common/clauses-1.c: Adjust.
	* testsuite/libgomp.oacc-c-c++-common/nested-1.c: Adjust.

From-SVN: r279145