Handle --packager-config in zypp_rpm

This is an attempt to handle a different --reposd-dir in the zypp_rpm
driver. Up to now the system repositories in /etc/zypp/repos.d were
used.

To specify a different set of repositories for zypp a parser for a
simple zypper.conf is added in this patch. It just looks for reposdir=
in section main, like this:

 [main]
 reposdir=/path/to/other/repofiles

If the config file provided via "--packager-config my_zypp.conf" is
valid the other directory is passed to zypper, otherwise the system
repos.d is used like its done in current code.

Depending on the kind of provided repos, the current code may fail to
import a repo in non-interactive mode. This happens if the repo data are
not properly signed. For this reason the option --no-gpg-checks is added
by this patch.

Finally, the parser uses ocaml-inifiles to read the config file. This is
a new build dependency. inifiles should be available in various
distributions, copies of the original sources can be found via google.

This patch has received some light testing, I sent it out to the list
for further comments. Particular about the new inifiles dependency..

Signed-off-by: Olaf Hering <olaf@aepfle.de>
zypp: Trailing whitespace.
zypp: Only compile zypper support if OCaml inifiles module is found.