This effectively eliminates all use of MMX instructions, using SSE ones
instead.

Bug swiftshader:78

Change-Id: I3e519a0c5172688ff711654bf430a9d1dd058d0b
Reviewed-on: https://swiftshader-review.googlesource.com/11049Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>