Requested off-list.
Trivial to add and more importantly trivial to test.

ANDNL
ANDNQ
BEXTRL
BEXTRQ
BZHIL
BZHIQ
MULXL
MULXQ
PDEPL
PDEPQ
PEXTL
PEXTQ
SARXL
SARXQ
SHRXL
SHRXQ

Change-Id: I3d46a0f653b81dd003ff6d2a394d8ce96a573b63
Reviewed-on: https://go-review.googlesource.com/18857Reviewed-by: Rob Pike <r@golang.org>