We require a libgda-compat package because a lot of GNOME apps are
switching to the new stable 4.0 API (anjuta, glom), but there are 
still a lot of applications which haven't made this non-trivial
update.  The compat package is available for those applications, 
which offers the previous stable 3.0.5 API which can be installed 
alongside libgda-4.0.