* stmt.c (n_occurrences): New static function.
        (expand_asm_operands): Verify that all constrains match in the
        number of alternatives.
        Verify that '+' or '=' are at the beginning of an output constraint.
        Don't allow '&' for input operands.
        Verify that '%' isn't written for the last operand.
        * reload.c (find_reloads): Abort if an asm is found with invalid
        constraints; all possible problems ought to be checked for earlier.

From-SVN: r22911