ppc64/ppc64asm,ppc64/ppc64map: fixes for ppc64 disassembly

This adds some fixes to the ppc64 disassembly:
- Add support for VSX registers, by updating the map
function to recognize them, regenerating tables.go
to include them with VSX instructions, and adding the
defines needed to display them correctly.
- Change the path to the system objdump in the testcase
for use in comparing the decoded machine instructions.
- Add mappings for missing opcodes in plan9.go.
- Disable the testcase that generates words with random
bit settings for use in decoding. This will be replaced
later by an assembler testcase that decodes and compares
the result with the system objdump.

Fixes golang/go#17447

Change-Id: I23bf276ea7fcf0b54abb3dccca8b41c221c81c94
Reviewed-on: https://go-review.googlesource.com/31146
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
8 files changed