libtiff comes with this godawful tiff viewer called tiffgt, which is written
(for reasons no-one can fathom) using OpenGL.  It doesn't seem to offer any real
redeeming features, and breaks easily (it segfaulted on a sample tiff I created
in gimp).

Can we chop this bit out of the build so this dependancy goes away ?
I noticed it when I installed samba on a fileserver, and saw it trying to pull
in GL libraries on a headless box via  samba-common->cups-libs->libtiff->mesa-libGL