libgnomecanvas defines no GType for GnomeCanvasPathDef, even though simple
boxed type support would be trivial to add.

In the absence of a proper GType, the bpath property of GnomeCanvasBpath is
created as a G_TYPE_POINTER, making it impossible to use this property
through languange bindings.  (By impossible, i mean it tries to work, but
crashes horribly.)

This bug results in core dumps when attempting to set the bpath property in
gtk2-perl through standard methods.  The workaround is to offer set_path
and get_path methods at the binding level, but there is no way to protect
unsuspecting binding users from the crash if they attempt to use the
property interface.

I marked this as affecting CVS HEAD, but it's in all versions of
libgnomecanvas i could find.