re PR middle-end/15885 (wrong va_start warning (and code))

        * cp-lang.c (cxx_types_compatible_p): To the middle-end,
        references and pointers are compatible.

        PR middle-end/15885
        * gimplify.c (gimplify_arg): New fn, split out from...
        (gimplify_call_expr): Here.  Special-case BUILT_IN_VA_START.

From-SVN: r84782