Changeset 2633 for code/branches/buildsystem2/cmake

Added documentation target. Surprisingly worked on my box just like that. I had to limit the input files to /src (source and binary tree) though, or Doxygen would have created for all the dependencies as well (boost, ogre, etc.) because of the dependencies folder.

Note: This is all just copy & paste from the CMake forum. I haven't had a look at it.
Somebody will have to merge our own Doxyfile with the new one.