Significantly reduce number of IsMaskedAway calculations

[smoogipoo]

Reduces anywhere from 1.5-2.5K IsMaskedAway calculations, depending on the screen. Results in about 35-45 update fps boost (270/280 - 310/320) in gameplay (mania), about 30fps in SongSelect.

This would've previously been computed during drawnode creation only if we were present anyway (basically just before the IsMaskedAway check in addFromComposite).

[Tom94]

I have a feeling this may cause problems. UpdateSubTree is optimized based on IsMaskedAway, so non-present drawables may not get the updates they require to become present again if IsMaskedAway isn't updated correctly. Not 100% sure, though. May be an invalid point if UpdateSubTree is also optimized heavily via IsPresent.

[smoogipoo]

UpdateSubTree is indeed heavily optimised through IsPresent, and arguably much less optimised through IsMaskedAway.

[smoogipoo]

If you're still unsure about this, I'll also bring up again that this was essentially previous behaviour - IsMaskedAway previously only got computed in addFromComposite, following the IsPresent check in there.