OpenMP: allow requires dynamic_allocators

There's no need to reject the dynamic_allocators requires directive because
we actually do support the feature, and it doesn't have to actually "do"
anything.

gcc/c/ChangeLog:

	* c-parser.c (c_parser_omp_requires): Don't "sorry" dynamic_allocators.

gcc/cp/ChangeLog:

	* parser.c (cp_parser_omp_requires): Don't "sorry" dynamic_allocators.

gcc/fortran/ChangeLog:

	* openmp.c (gfc_match_omp_requires): Don't "sorry" dynamic_allocators.

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/requires-8.f90: Reinstate dynamic allocators
	requirement.

gcc/c/c-parser.c

@@ -22583,7 +22583,7 @@ c_parser_omp_requires (c_parser *parser)
 	      c_parser_skip_to_pragma_eol (parser, false);
 	      return;
 	    }
-	  if (p)
+	  if (p && this_req != OMP_REQUIRES_DYNAMIC_ALLOCATORS)
 	    sorry_at (cloc, "%qs clause on %<requires%> directive not "
 			    "supported yet", p);
 	  if (p)

gcc/cp/parser.c

@@ -46512,7 +46512,7 @@ cp_parser_omp_requires (cp_parser *parser, cp_token *pragma_tok)
 	      cp_parser_skip_to_pragma_eol (parser, pragma_tok);
 	      return false;
 	    }
-	  if (p)
+	  if (p && this_req != OMP_REQUIRES_DYNAMIC_ALLOCATORS)
 	    sorry_at (cloc, "%qs clause on %<requires%> directive not "
 			    "supported yet", p);
 	  if (p)

gcc/fortran/openmp.c

@@ -5412,7 +5412,8 @@ gfc_match_omp_requires (void)
       else
 	goto error;
 
-      if (requires_clause & ~OMP_REQ_ATOMIC_MEM_ORDER_MASK)
+      if (requires_clause & ~(OMP_REQ_ATOMIC_MEM_ORDER_MASK
+			      | OMP_REQ_DYNAMIC_ALLOCATORS))
 	gfc_error_now ("Sorry, %qs clause at %L on REQUIRES directive is not "
 		       "yet supported", clause, &old_loc);
       if (!gfc_omp_requires_add_clause (requires_clause, clause, &old_loc, NULL))

gcc/testsuite/gfortran.dg/gomp/requires-8.f90

@@ -4,7 +4,7 @@ contains
  subroutine foo
   interface
    subroutine bar2
-     !$!omp requires dynamic_allocators
+     !$omp requires dynamic_allocators
    end subroutine
   end interface
   !$omp target