Additions:
MultiWindowLockStepTest([nrwins=10][, separateScreens=0]);
If set to [], 2 windows will be used. The i'th window is flipped
If the optional parameter 'separateScreens' is set to a non-zero
setting, then the different onscreen windows are not opened
on the same display screen 0, but each one on a separate screen.
Performance can differ significantly between one screen and
multi-screen, as the operating system will use very different
underlying algorithms and methods to handle flips on windows,
depending on their placement on different displays or not. Each
operating system will also behave differently.
Deletions:
MultiWindowLockStepTest([nrwins]);
If set to [], 10 windows will be used. The i'th window is flipped