Magic Mask perf improvements

For certain cases, Magic Mask would be more of a candidate for ease of masking if it allowed one to choose various sections of a single comp to process with either the same Magic Mask, or multiple magic masks at once in parallel. This suggestion is based on observing only approximately 20% utilization of hardware as Magic Mask moves slowly linearly through a comp. This suggested perf improvement would make it easier to choose Magic Mask's power for at least cases where a single comp has sporadic interference by an object. Magic Mask is phenomenal but it's difficult to harness that power for some circumstances where the tedium to find/setup/perform N linear magic mask operations outweighs ease benefits. This suggestion is made based on what seems to be room to help magic mask make its way through a large comp much faster. Temper my +1: not a huge priority, but certainly would be used. It seems like others really like MM power but get hit with perf issues as well.