I took a look at your xscreensaver packages. Some comments:
I don't see why you patch hacks/speedmine.c; the optimization you make
(turning a division by two into a right bitshift by 1) is generally
going to be made by GCC anyways.
Your diff includes po/.intltool-merge-cache, which probably isn't
intentional.
Now, you should change the version number to 4.05-1.1, since this is a
NMU. I suggest just merging all your changelog entries since Colin
Watson's upload together, since they weren't actually part of Debian.
Finally, there are a lot of open bugs against xscreensaver. Could you
go through some of the list and see which ones are closed by this new
upstream version? I imagine a lot of them will be.