openmp: Provide fixit hints for -Wdeprecated-openmp diagnostics from C++ FE

I think especially the linear clause -Wdeprecated-openmp diagnostics
will be complete nightmare for users, when they have
linear (ref (x, y, z))
or
linear (uval (a, b, c) : 2)
they will have no clue what the new syntax is.

Here is an attempt to provide fixit hints from the C++ FE for most
of these warnings, and even -fdiagnostics-generate-patch can then be
useful for porting.

2025-12-13  Jakub Jelinek  <jakub@redhat.com>

	* parser.cc (cp_parser_omp_clause_reduction): Provide fixit hints
	for -Wdeprecated-openmp diagnostics.
	(cp_parser_omp_clause_linear): Likewise.
	(cp_parser_omp_clause_depend): Likewise.
	(cp_parser_omp_clause_map): Likewise.  Reset num_commas after the
	diagnostics.
	(cp_parser_omp_clause_proc_bind): Provide fixit hints for
	-Wdeprecated-openmp diagnostics.
	(cp_parser_omp_all_clauses): Move -Wdeprecated-openmp diagnostics
	for to vs. enter here, add fixit hints for it.
	(cp_parser_omp_master):Add MASTER_LOC argument.  Provide fixit hints
	for -Wdeprecated-openmp diagnostics.
	(cp_parser_omp_parallel): Adjust cp_parser_omp_master caller.
	(cp_parser_omp_declare_target): Don't emit -Wdeprecated-openmp
	warning for to vs. enter here.
	(cp_parser_omp_metadirective): Provide fixit hints for
	-Wdeprecated-openmp diagnostics.
	(cp_parser_omp_construct): Adjust cp_parser_omp_master caller.

	* g++.dg/gomp/deprecate-1.C: New test.