* glib/Makefile.am : add new file.
* glib/Object.cs : add protected PersistentData hash to hold data
across GC cycles.
* glib/WeakObject.cs : new object to hold managed refs weakly against
the native object.
* gtk/ListStore.custom : hold refs for DefaultSortFuncs.
* gtk/TreeModelSort.custom : hold refs for DefaultSortFuncs.
* gtk/TreeStore.custom : hold refs for DefaultSortFuncs.
svn path=/trunk/gtk-sharp/; revision=41740