libkate: dependency fixes

Does anyone actually use this package? I’m amazed nobody has noticed
it’s been really quite broken for a while. It hasn’t been building the
ogg libraries because it finds that dependency through pkg-config which
we hadn’t specified as a dependency, and the only other thing that
hooks into libkate looks for those ogg libraries and fails to find
those consequently. This also adds optional dependencies for
documentation, examples and the GUI for libkate. Libogg also isn’t
really a recommended dependency, if we’re going with libpng being
mandatory libogg should be as well.

Added a mirror and a simple test as well.
libkate: update 0.4.1_1 bottle.