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

[Kazu Hirata]

Hi Mark,

> > > Attached is a patch to replace "return NULL_RTX" with "return 0".
> > >
> > > In the past, there were some arguments to prefer 0 to NULL_RTX, such
> 
> Like Jason, I prefer NULL to 0.  
> 
> But not enough to really argue about it... :-)

I guess we should leave the issue as is for now. :-)

Kazu Hirata