Code Merge Request #1: bb: Fix z-buffer overflow on 64-bit systems (open)

The z-buffer is an int array allocated with sizeof(int) per pixel, but clear_zbuff cleared sizeof(long) per pixel, writing past the end of the buffer on LP64 systems every frame of scene 5. This corrupted the heap or, once the buffer was large enough to be mmapped (a terminal of about 200x50 or more), segfaulted right away.