Disassembler:
added decoding of a few instructions that were previously unsupported, fixed the decoding of pextr.

Assembler:

pmulld(XMMRegister, Operand) was actually emitting a pmuludq.

punpckldq(XMMRegister, XMMRegister) was implemented a second time as punpackldq.

BUG=

Review-Url: https://codereview.chromium.org/2070863002
Cr-Commit-Position: refs/heads/master@{#37059}