Update to Git v1.8.5.2
Update patch to account for Git changes

Git upstream has effectively incorporated part of our
1.7.9-cygwin.patch.  Rewrite that patch to only include the bits it
still needs.
Remove python from Cygport inherited Cygclasses

Having Python in the Cygclasses stopped the step of building the
packages from completing, and removing it doesn't seem to cause any
problems as far as I can tell.  I suspect it was previously necessary
for something that's no longer part of Git.
Go get the source from the original source

Get the source code from the original upstream Git repository.  Slower
but should hopefully be less likely to disappear or fall out of sync
than the Google code repository.
Update .gitignore for new src source