* generator/GObjectGen.cs: Added new generatable to handle
plain GObjects the same way we do subclasses.
* generator/ManualGen.cs: Make FromNative/FromNativeReturn virtual
to allow overriding.
* generator/SymbolTable.cs: Use GObjectGen instead of
ManualGen for GObject.
* generator/Makefile.am: Add GObjectGen.cs.
svn path=/trunk/gtk-sharp/; revision=25651