OpenMP: Accept argument to depobj's destroy clause

OpenMP: Accept argument to depobj's destroy clause

Since OpenMP 5.2, the destroy clause takes an depend argument as argument;
for the depobj directive, it the new argument is optional but, if present,
it must be identical to the directive's argument.

gcc/c/ChangeLog:

	* c-parser.cc (c_parser_omp_depobj): Accept optionally an argument
	to the destroy clause.

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_omp_depobj): Accept optionally an argument
	to the destroy clause.

gcc/fortran/ChangeLog:

	* openmp.cc (gfc_match_omp_depobj): Accept optionally an argument
	to the destroy clause.

libgomp/ChangeLog:

	* libgomp.texi (5.2 Impl. Status): An argument to the destroy clause
	is now supported.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/depobj-3.c: New test.
	* gfortran.dg/gomp/depobj-3.f90: New test.