"No change" rebuilds and archive skew

[Scott Kitterman]

Yesterday I had to re-upload gdk-pixbuf and atk1.0 to pick up the new gobject-
introspection on powerpc.  This enabled a reasonable number of powerpc FTBFS 
(~half a dozen) to be fixed.

It looks like when they were initially uploaded, gobject-introspection was 
built on amd64, armel, and i386, but not powerpc and as a result, these 
packages ended up incorrectly built against the older gobject-introspection on 
just powerpc.  Misbuilds like this can be difficult to detect.

Please: If you aren't going to wait until the library you are rebuilding 
against is built on all architctures, add a minimum version to the build-
depends so that it won't build against the wrong one on slower architectures.

Scott K