OpenMP/Fortran: Add support for firstprivate and allocate clauses on scope construct

OpenMP/Fortran: Add support for firstprivate and allocate clauses on scope construct

Fortran commit to C/C++/backend commit
r13-862-gf38b20d68fade5a922b9f68c4c3841e653d1b83c

gcc/fortran/ChangeLog:

	* openmp.cc (OMP_SCOPE_CLAUSES): Add firstprivate and allocate.

libgomp/ChangeLog:

	* libgomp.texi (OpenMP 5.2): Mark scope w/ firstprivate/allocate as Y.
	* testsuite/libgomp.fortran/scope-2.f90: New test.

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/scope-5.f90: New test.
	* gfortran.dg/gomp/scope-6.f90: New test.

(cherry picked from commit ff35a75473d28205e52ecbcf9e6b5107b8b5ab90)