* target.h (struct gcc_target): Change gimplify_va_arg_expr
        hook signature.
        * tree-gimple.h: Adjust.
        * config/alpha/alpha.c (alpha_gimplify_va_arg): Adjust.
        * config/i386/i386.c (ix86_gimplify_va_arg): Adjust.
        Use fold_convert.
        * config/ia64/ia64.c (ia64_gimplify_va_arg): Adjust.
        * config/rs6000/rs6000.c (rs6000_gimplify_va_arg): Adjust.
        Use COMPLEX_EXPR for complex numbers.  Use fold_convert.
        * builtins.c (std_gimplify_va_arg_expr): Adjust.  Use fold_convert.
        (gimplify_va_arg_expr): Return GS_ERROR in error case.
        Gimplify valist rather than calling stabilize_va_list.

From-SVN: r82925