OpenMP: Check additional restrictions on context selector properties

TR13 (pre-6.0) of the OpenMP spec says:

"Each trait-property may only be specified once in a trait selector
other than those in the construct selector set."

and

"If trait-property any is specified in the kind trait-selector of the
device selector set or the target_device selector sets, no other
trait-property may be specified in the same selector set."

These restrictions (with slightly different wording) date back to
OpenMP 5.1, but were not in 5.0 which was the basis for GCC's
implementation.

This patch adds a diagnostic, adds new testcases, and fixes some older
testcases that include now-invalid selectors.

gcc/ChangeLog
	* omp-general.cc (omp_check_context_selector): Reject other
	properties in the same selector set with kind(any).  Also reject
	duplicate name-list properties.

gcc/testsuite/ChangeLog
	* c-c++-common/gomp/declare-variant-10.c: Fix broken tests.
	* c-c++-common/gomp/declare-variant-3.c: Likewise.
	* c-c++-common/gomp/declare-variant-9.c: Likewise.
	* c-c++-common/gomp/declare-variant-any.c: New.
	* c-c++-common/gomp/declare-variant-duplicates.c: New.
	* gfortran.dg/gomp/declare-variant-10.f90: Fix broken tests.
	* gfortran.dg/gomp/declare-variant-3.f90: Likewise.
	* gfortran.dg/gomp/declare-variant-9.f90: Likewise.
	* gfortran.dg/gomp/declare-variant-any.f90: New.
	* gfortran.dg/gomp/declare-variant-duplicates.f90: New.