round(...) is defined in Visual C++ 2013; added as exception to preprocessor fix
demo-cube's timer-callback wasn't working because of bug in GLUT (see references below); changed to use clock() instead

References:
- http://stackoverflow.com/questions/19133222/gluttimerfunc-callback-function-isnt-executed-if-time-threshold-is-under-a-ce
- http://www.opengl.org/discussion_boards/showthread.php/164209-glutTimerFunc-issues-with-Vista