treeview: Adds BeginUpdate / EndUpdate support.
treeview: Adds BeginUpdate / EndUpdate support.

This drastically improves performance, if you have some code that
iterates and updates all nodes.

wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI