[Patch] OpenMP: Document ompx warnings + add Fortran omx warning [PR106670]

(Patch + RFC.) OpenMP 5.2 has 'ompx' and (for fixed source form Fortran) 'omx' as sentinel to provide a defined namespace for vendor extensions. The behavior when encountering an unknown directive with ompx/omp sentinel (or an unknown clause with ompx_ prefix) is implementation defined. For unkn

Re: [Patch] OpenMP/Fortran: Permit end-clause on directive

Hi Tobias, this is not really a review, but: Am 26.08.22 um 20:21 schrieb Tobias Burnus: I did run into some issues related to this; those turned out to be unrelated, but I end ended up implementing this feature. Side remark: 'omp parallel workshare' seems to actually permit 'nowait' now, but