Fixes #311955, reported by Markku Vire; and a lot more.

Fixes #311955, reported by Markku Vire; and a lot more.

2005-10-25  Kristian Rietveld  <kris@gtk.org>

	Fixes #311955, reported by Markku Vire; and a lot more.

	* gtk/gtktreemodelfilter.c: Made this thing work correctly.
	Levels can now have invisible nodes cached, functions have been
	rewritten/refactored to take this into account; also the logic in
	some functions has been corrected.

	Each referenced node now references all visible children or a single
	invisible child, in order to be able to monitor all changes in the
	child model required for correct operation.

	When a virtual root is set, all nodes on the virtual root level are
	referenced.

	At last, a bunch of random bug fixes and comment updates.