Update all examples to work on OSX

This updates all examples to at least compile and run on OSX.

Note that I got the following error in ogl3-prerend though (it still ran):

!!!!! OpenGL Error !!!!! invalid enumerant - occurred before /Users/belak/opengl-examples/ogl3-prerend.c:57

Changes that may seem a little odd:

• FindGLUT.cmake - This was updated to a newer version of the file to fix an error relating to CMake trying to include Xi and Xmu on OSX. The paths /usr/local/include and /usr/local/lib were added to the respective locations (I think those were the only changes path wise? Please correct me if I'm wrong here.)
• CMakeLists.txt - We don't need freeglut on OSX. It's just the glut that comes with XCode. There are quite a few deprecation warnings though. This will probably have to change in a few years.

I tested all the examples at least once, simply to check if they ran. I can't make any promises (for sure) about them acting the same across platforms though as I haven't really seen them run on Ubuntu.