[patch] alias.c: Replace "return NULL_RTX" with "return 0".

[Kaveh R. Ghazi]

 > > A system that defines NULL to 0 where that is a different size from
 > > (void*)0 is broken.  Does such brokenness actually exist?
 > 
 > Dunno, but that's still not good enough - consider an ABI where
 > pointers go in different registers from integers when passing
 > arguments.
 > zw

I thought variadic function introduce extra overhead to avoid this
issue.  (E.g. don't pass in registers.)  Otherwise how would va_arg
know where to get the data from?

--
Kaveh R. Ghazi			ghazi@caip.rutgers.edu