Requied for constrained Delaunay triangulation (P&S/ratsnest) and zone tesselation (GAL).

Changed VIEW::PrepareTargets() to more appropriate name VIEW::ClearTargets(). Added SELECTION layer to always-on-top list.

Mouse movement events are sent during autopanning, as the cursor position changes in the world coordinates (even if it stays still in the screen coordinates). It allows tools to update their state, as if the mouse was moved.