The upstream changelog is generated during the upstream release
process, but expected when building the binary .debs. Make its
inclusion optional in the binary .debs.
This reverts commit 0cb518bc5a and fixes
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=595883
The changelog MUST not be generated during the Debian package build as
it relies on a checked out copy of the VCS repository -- what the
Debian package isn't. The Debian (and any other packaging) gets the
changelog from our tar.gz balls.
We will have to fix the issue, which the reverted commit tried to fix,
differently.