The ptrace get and set methods for VMX/Altivec registers present in the
ppc tree were missing for ppc64.  This patch adds the 32-bit and
64-bit methods.  Updated with the suggestions from Anton following the lines
of his code snippet.

Added:
 - flush_altivec_to_thread calls as suggested by Anton
 - piecewise copy of structure to preserve 32-bit vrsave data as per
   Anton

(I consolidated the 32 and 64bit versions with 2 helper macros - Anton)
Signed-off-by: NRobert C Jennings <rcjenn@austin.ibm.com>
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!