MFC	r250550:
Update the gcc43 changelog.

The issue solved in r250515 actually originated upstream and was
fixed in upstream gcc43 branch in 2006/10/24 (under GPLv2).

Register it in the appropriate ChangeLog for reference.
MFC r250393:

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 r246711:

o Bring in sync decoding the first nfssvc(2) parameter (flags) with
the current definitions location.
o Respect numbers in NFSSVC_* (e.g. NFSSVC_V4ROOTEXPORT).
MFC r248250-248251:

- Add the getcontextx prototype to SYNOPSIS.
- Link getcontextx(3) to getcontext(3).