build-xbmc.sh updated for patchlevel 2

The build script does not rely on the xbmc PPA anymore, except for libshairplay-dev.

The original packages get pulled from libregeek.org now.

The install procedure was updated and should now reflect a complete build of patch-level 2 xbmc packages.

Deleted section "Miscellaneous Stuff", it's all done in RetroRig aynway.

Please note: This has nothing to do with the latest debug version for testing #45! If this debug version turns out to be a valid solution, it will be patch level three.