openmp: Diagnose using grainsize+num_tasks clauses together [PR115103]

openmp: Diagnose using grainsize+num_tasks clauses together [PR115103]

I've noticed that while we diagnose many other OpenMP exclusive clauses,
we don't diagnose grainsize together with num_tasks on taskloop construct
in all of C, C++ and Fortran (the implementation simply ignored grainsize
in that case) and for Fortran also don't diagnose mixing nogroup clause
with reduction clause(s).

Fixed thusly.

2024-05-15  Jakub Jelinek  <jakub@redhat.com>

	PR c/115103
gcc/c/
	* c-typeck.cc (c_finish_omp_clauses): Diagnose grainsize
	used together with num_tasks.
gcc/cp/
	* semantics.cc (finish_omp_clauses): Diagnose grainsize
	used together with num_tasks.
gcc/fortran/
	* openmp.cc (resolve_omp_clauses): Diagnose grainsize
	used together with num_tasks or nogroup used together with
	reduction.
gcc/testsuite/
	* c-c++-common/gomp/clause-dups-1.c: Add 2 further expected errors.
	* gfortran.dg/gomp/pr115103.f90: New test.