GitLab

The Makefile will now use a script (autoversion.sh) to update
version.h, which in turn defines a VERSION string and gets
included from common.h.

The idea is that version.h normally receives a git-describe
based identifier that represents the current checkout. In
cases where git might not be available, e.g. for builds from
a tarball, the script will instead fall back to a predefined
version (that should reflect the most recent release tag).
Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>