Changed to indirect call of setUp and tearDown functions.
* Created "typedef void (*unity_void_fn)(void)"
* Created members of struct _Unity of unity_void_fn type that points to setUp and tearDown
* Added parameters of UnityBegin: pointers to setUp and tearDown, so as to setup the pointers in struct _Unity Unity
* Changed auto/generate_test_runner.rb so as to generate test runners that uses pointers to setUp and tearDown istead of direct calls.