First 4.6-alpha image available for download

http://ftp.squeak.org/4.6alpha/Squeak4.6-13700.zip

This includes the condensed sources and empty changes file.

I really wanted us to have the prior versions --all during the
development cycle--, but I don't see any way for that to be feasible.
The image that creates the new sources file has the proper
file-pointers into that new file, and so the eventual release image
must be a descendant of that.

So compressSources has to run at the beginning, instead of the end, of
the dev cycle.  :(