OSX Path Additions

I personally don't use homebrew, so my libfreenect gets installed in to /usr/local instead of /usr by the cmake install target. I fixed this by adding the right include and library paths to the the Freenect driver makefile.

It's also worth noting that if you install libfreenect with cmake built from source, then you have to build it as a universal binary or OpenNI won't link. You can do this by setting `CMAKE_OSX_ARCHITECTURES=i386;x86_64` when running ccmake.

After building libfreenect as a universal binary and OpenNI with the path changes, I was able to get all of the samples working, as well as set up an Xcode project to build my own OpenNI-based application. I just added a "Copy Files" rule to the build rules and copied the libOpenNI binary and OpenNI folder from the Samples directory to Xcode's "Executables" location. Then its just a matter of linking in the binary like you would any other library.