Picture flash doesn't work on lower layers

[mateofio]

Because of the way we blit flash effects to the screen, pictures on layers below weather misbehave.

The left are all layers unaffected by flash, the right affected by flash.

All the clouds are supposed to look like the bottom row.

[mateofio]

I thinking for this one. Maybe the optimal solution is:

1. In z order render all drawables that are affected by flash, without the effect, until the first one that isn't.
2. Render flash on the entire display
3. Now render remaining drawables in Z order, flashing each one individually if it's affected.

For most games which don't use lower layer pictures unaffected by flash, this would maintain the optimization we currently have.

The same can be done for tone.