[RFA] mips_push_arguments(): Make O64 ABI test explicit

[Andrew Cagney]

> Sounds like the comment should be updated to mention a few more ABIs and 
>> confirm that it is GCC that is wrong.   I'll assume this patch is withdrawn.
> 
> 
> It is for the moment.
> 
> If you read further in the thread, you'll see that I've verified that
> it's gcc which is wrong.

I did, that is why I suggested ``confirm that it is GCC'' :-)

> That being the case, more than just the comment
> will need to change.  (IMO, of course.)

In what way?  GDB was trying to implement things according to the ABI 
(unless someone snuck in a change or the code suffered bit rot).

As DanielJ mentioned, GCC should be fixed.

> I'll wait a bit for further discussion before submitting a new patch.

Andrew