* Makefile.am: reenable samples.
* sample/Actions.cs: s/Item/MenuItem, Item is dead.
* sample/NativeInstantiationTest.cs: fix dllimport, still crashes.
* sample/PolarFixed.cs: Fix size negotiation API usage, still crashes.
* sample/TreeModelDemo.cs: add ItemPrevious, still crashes.
* sample/Makefile.am: comment out some samples that don't build.
* glib/Object.cs: add support for native instantiation of
managed types.
* glib/ParamSpec.cs: add Flags ctor overload.
* sample/NativeInstantiationTest.cs: new sample to test the
unmanaged instantiation capability.
Based on a patch from Sebastian Dröge [Fixes#499900]
svn path=/trunk/gtk-sharp/; revision=141819