-Removed a few extra unneeded virtuals
-Pulled tabgroups out of llpanel and into LLView
-removeChild doesn't support delete. Delete manually.
-addChildAtEnd renamed to addChildInBack
-getScreenRect renamed to calcScreenRect
-added calcScreenBoundingRect and calcBoundingRect(which updateBoundingRect calls
-General cleanup. Someone at LL figured out that dynamic_cast actually exists.
Fixed PieMenu not reliably centering on cursor.
Fixed context menu crash in line and text editors.
Classes with LLEditMenuHandler as a base do not need to set gEditMenuHandler to NULL, since LLEditMenuHandler's dtor does that already!
