bug fix for c-torture test execute/bf-sign-2.c

[Joern Rennecke]

>   > Wed Oct 22 14:08:50 1997 J"orn Rennecke <amylaar@cygnus.co.uk>
>   > 
>   > 	* execute/bf-sign-2.c (struct X): New member u15.
>   > 	(main): Check u15.  Check for u31 depends on size of int.
> I don't remember this failing for the mn10200, which is a 16bit int
> target.  Maybe you should describe why it's failing on yours so that
> we can understand your patch.

P.S.: I just checked mn10200.h - long long is 32 bits, so presumably the
test is skipped.
Maybe we should also add a long long - free version of the test, so that
the h8300 and mn10200 get coverage.