OpenGLSample crash fix

## Bug ##
When closing the window in Windows while using Visual Studio, the sample program will crash trying to free memory that was already freed.

## Cause ##
Order of operations was causing the crash. The OpenGL renderer was being deleted first, then the TexturedBase skin at the end of main(), since it was a local variable. The crash would then occur because the skin which depended on the freed renderer.

## Fix ##
skin was changed to a pointer, allowing it to be deleted before the OpenGL renderer.

## Misc Changes ##
Added a newline to the end of OpenGLSample.cpp to avoid GNU compiler warnings.