Backport from mainline

Backport from mainline

2019-09-20  Tobias Burnus  <tobias@codesourcery.com>

        * openmp.c (gfc_resolve_oacc_declare): Reject all
        non variables but accept function result variables.
        * trans-openmp.c (gfc_trans_omp_clauses): Handle
        function-result variables for remaing cases.

2019-09-20  Tobias Burnus  <tobias@codesourcery.com>

        * gfortran.dg/goacc/parameter.f95: Change
        dg-error as it is now detected earlier.
        * gfortran.dg/goacc/pr85701.f90: Modify to
        use a separate result variable.
        * gfortran.dg/goacc/pr78260.f90: New.
        * gfortran.dg/goacc/pr78260-2.f90: New.
        * gfortran.dg/gomp/pr78260.f90: New.
        * gfortran.dg/gomp/pr78260-2.f90: New.
        * gfortran.dg/gomp/pr78260-3.f90: New.

(cherry picked from openacc-gcc-9-branch commit
7d0d394c1c9bfb1b489c4ad3bd606d7a4765ae1d)