Initial Patch submitted by Christian Hoff with some small
style alterations and a round trip sample by me. Supports the
registration of managed properties with the GType system, so
that things like custom cell renderers can be accessed via the
native property system from treeview.
* glib/glue/object.c : property registration related glue.
* glib/Object.cs: implement managed property registration.
* glib/PropertyAttribute.cs: add new props and ctor for managed
property registration.
* sample/PropertyRegistration.cs: little test app to test round-
tripping of registered properties.
* sample/Makefile.am: add new sample.
svn path=/trunk/gtk-sharp/; revision=105177
