gimplify.c (gimplify_call_expr): Make return in memory explicit.

        * gimplify.c (gimplify_call_expr): Make return in memory explicit.
        (gimplify_modify_expr_rhs): Likewise.
        * c-common.c (c_warn_unused_result): Check TREE_USED before
        warning about a CALL_EXPR with an unused value.

From-SVN: r85671