Log Message:
goocanvas2: update to 2.0.4.

GooCanvas 2.0.4	(Oct 10 2017)
===============

 o Support latest gtk-doc and add an index #788436.

GooCanvas 2.0.3	(Aug 30 2017)
===============

 o Fixed stuck pointer grab bug #711709.
 o Fixed several introspection problems.
 o Removed use of a lot of deprecated GTK+ API.

GooCanvas 2.0.2	(Nov 3 2013)
===============

 o Fixed the drawing code to work with GTK+ 3.10.
 o Added/fixed a few introspection flags. GooCanvasLineDash should now be
   usable via introspection.