Fix push_arguments on x86-64

[Mark Kettenis]

Andreas Jaeger <aj@suse.de> writes:

> Ok to commit to both mainline and 6.0 branch?
> 
> 2003-06-26  Andreas Jaeger  <aj@suse.de>
> 
> 	* x86-64-tdep.c (x86_64_push_arguments): Always set %rax to number
> 	of SSE registers so that varargs functions work.
> 	Rework handling of passing arguments on the stack.

I believe that the whole argument classification functionality is more
complex than it needs to be based on reading the ABI, but it seems to
be an improvement and I trust you know what you're doing, so yes, this
is approved.

Mark