Merge pull request #264 from euanh/build-improvements

debian: Switch from pbuilder to cowbuilder
Merge pull request #265 from euanh/build-improvements

debian: Fix leftover references to BASETGZ
Merge pull request #266 from euanh/build-improvements

debian: cowbuilder doesn't seem to honour EXTRAPACKAGES with --create
Merge pull request #267 from euanh/build-improvements

debian: Prevent apt from calling fsync after each package installation
Merge pull request #268 from euanh/build-improvements

debian: Switch to gdebi dependency resolver
ocaml-camomile: Update to 0.8.5

Ubuntu insists on installing its v0.8.4 package ahead of
our v0.8.3 one, so lets update to 0.8.5 and trump it.

Signed-off-by: Euan Harris <euan.harris@citrix.com>