PowerPC Altivec version of setjmp/longjmp

[Joel Sherrill]

Eric Norum wrote:
> The code in powerpc/setjmp.S contains conditionally assembled code 
> which saves/restores the Altivec registers.  This breaks on operating 
> systems like RTEMS which do not normally enable the Altivec unit.  The 
> RTEMS maintainers asked me to submit this patch which was originally 
> provided by Till Straumann  <strauman@slac.stanford.edu>
> The patch is quite small so I've just attached it to this message.

There haven't been any comments on this.

Just because the CPU supports a feature doesn't mean it is enabled.
This patch just honors that.  Please consider merging it.

Thanks.

--joel sherrill