powerpc support for compat_sa.c

[matthew green <mrg%eterna.com.au@localhost>]

i haven't tested actual SA apps, but this links and runs for a modern
userland at least.

        ftp.netbsd.org:/pub/NetBSD/misc/mrg/powerpc.sa.diff

can some ppc person review and/or commit this?

thanks.


.mrg.