[gtkmm] Compatibility bug 2.0 -> 2.4 - Treeview only

[Alberto Paro <alberto paro homeunix org>]

I notice a segfault if there are 2.0 and 2.3 gtkmm installed in the same
machine.
The segfault happens during depends resolution run-time.
For example if we use gtkmm and vfsmm (compiled against gtkm2.0) in the
same project AND we use a treeview (other widgets works).
Segfault happens during appending row.

A solution hack is to remove gtkmm2 libs and make symlinks to these.

Hi,
	Alberto