gdk3-gi: merge changes in gdk3
gdk3: rename to gdk3-no-gi
gdk3-gi: rename to gdk3
gdk3-no-gi: remove from build target
gdk3: split loader
glib2: fix free function
gdk3: support Gdk::Color.new
gdk3: support constants in Gdk::Event
gi: support instantiating union
gdk3: support Gdk::EventAny