CellRenderer: Draw selected items with STATE_SELECTED

So that the selection and the colors will be drawn properly,
similar to other cell renderers.

Change-Id: I3f4d1c973b301a18ed2b0849eb5664709e4f022d
kiwi: avoid depending on gobject

This makes it possible to use parts of kiwi without
requiring gobject.

Change-Id: I6d5ab9bb7ce0d128dc858271d804b3a73d710fa2