* gcc-interface/trans.c (struct language_function): Add GNAT_RET.
(f_gnat_ret): New macro.
(struct nrv_data): Add GNAT_RET.
(finalize_nrv_unc_r): New helper function.
(finalize_nrv): Add GNAT_RET parameter. Copy it into DATA. If the
function returns unconstrained, use finalize_nrv_unc_r as callback.
(return_value_ok_for_nrv_p): Test the alignment of RET_OBJ only if
RET_OBJ is non-null.
(Subprogram_Body_to_gnu): Pass GNAT_RET to finalize_nrv.
(gnat_to_gnu) <N_Return_Statement>: In the return-unconstrained case,
if optimization is enabled, record candidates for the Named Return
Value optimization.
From-SVN: r181528
