This patch fixes several problems:
1) Fixes the updates of the clone layer, when changing
   its source's mask
2) Fixes updates for undo of a transformation of a layer
   having both clone and a mask
3) Fixes Mirroring of a paint layer with odd size
4) Fixes Undo for transformations on Shape Layers
5) Adds a Unit Test for all this.

BUG:251168,312734,312742,312750