committed this change
An attempt at sorting out the various 64bit Windows builds.
IA64 indicates the Intel Itanium 64bit Windows build.
X64 indicates the AMD64 and the Intel EM64T 64bit Windows build.
It should not be necessary to set MSVCVer or OSPLAT for these builds.
Hopefully these changes didn't break the AMD64 Linux build.
p4transfer.py: Transferred from production
to cycle through the changes.