Fixes for snapshot building using bob. All of releases, snapshots

and custom svn builds should now have appropriately named Unix
source archives and installer binaries, plus .htaccess files
providing redirects to them from totally standard filenames. I
_think_ this now makes it feasible to switch the nightly builds to
using bob.

git-svn-id: svn://svn.tartarus.org/sgt/putty@7226 cda61777-01e9-0310-a592-d414129be87e