[Box-Admins] Added a Jenkins job for tracing a 64-bit image

[David T. Lewis]

I added one more Jenkins job called "Squeak 64-bit image". This will
hopefully be triggered each time the SqueakTrunk job runs. The output
is a copy of the trunk image traced to 64-bit object format.

I want to see this run for a few days before I mention it on the
squeak-dev list, but I think that this will give us an easy way
to maintain a 64-bit version of released images.

The build script is actually pretty cool, if you don't mind me saying
so. It used to take a lot of manual steps to trace an image to 64 bits
and clean up the resulting image to make it look like the original. But
this script automates the process with no cleanup required :)
The script is here:

    http://squeakci.org/job/Squeak%2064-bit%20image/ws/TraceTo64.st

Dave