For some reason, the gcc intrinsics header tmmintrin.h was imported with
two copies of itself pasted together.  Remove the extraneous copy.

MFC after:	3 days
When gcc 4.2.0 was imported, the 3DNow intrinsics header <mm3dnow.h> was
not added to the list of intrinsics headers to install, so belatedly (5
years :) add it.

MFC after:	1 week