Always force the git fetch remote URL

This makes it easy to switch the repo URL, like we'll have to do with
libass.

If you don't want this, edit the update script, I guess.
Switch libass repo to github

The Google Code one has been made invisible, because everyone is too
lazy to update it.
Merge remote-tracking branch 'origin/pr/18'
Fix bashism in debian/rules, handle errors better

POSIX sh requires a ';' before a closing ')'.
However, in this case the () were not even necessary,
so leave them out entirely (make already starts a separate
shell process for each command).

Also tidy up the whitespace a little to make things easier
on the eye.
debian changelog hack

put dummy UNRELEASED entry in changelog before build with dch -v
"version" "localbuild". This has the "papercut" of repeating the
"local build" bullet in the same entry each time the package is built.