OpenACC 1.0 fortran FE support -- translation to GENERIC.

     gcc/fortran/
     * trans-decl.c
     (gfc_generate_function_code): Insert OACC_DECLARE GENERIC node.
     * trans-openmp.c (gfc_convert_expr_to_tree): New helper function.
     (gfc_trans_omp_array_reduction): Support also OpenACC. Add parameter.
     (gfc_trans_omp_reduction_list): Update.
     (gfc_trans_oacc_construct): New transform function.
     (gfc_trans_omp_map_clause_list): Likewise.
     (gfc_trans_oacc_executable_directive): Likewise.
     (gfc_trans_oacc_combined_directive, gfc_trans_oacc_declare): Likewise.
     (gfc_trans_oacc_directive): Use them.
     (gfc_trans_oacc_loop): Stub.
     (gfc_trans_omp_clauses): Transform OpenACC clauses.
     * trans-stmt.h  (gfc_trans_oacc_directive): New function prototype.
     (gfc_trans_oacc_declare): Likewise.
     * trans.c (trans_code): Transform also OpenACC directives.