* generator/Makefile.am : remove source file.
* generator/Signal.cs : generate marshaling callbacks and use new
GLib.Signal marshaling class for events.
* generator/SignalHandler.cs : kill. byebye SignalCallback subclasses.
* glib/Makefile.am : update source files.
* glib/GLibSharp.voidObjectIntPtrSignal.cs : kill.
* glib/Object.cs : mark the old Before/After props Obsolete. Use
GLib.Signal for the notify prop methods.
* glib/Signal.cs : new signal marshaling class. It manages all the
ConnectBefore/After stuff internally and connects itself to the native
object using GCHandles and DestroyNotify lifecycle management.
* glib/SignalCallback.cs : mark Obsolete.
[Fixes#72018 and #69847]
svn path=/trunk/gtk-sharp/; revision=40007
