Read SVN Revision from git svn, too.

= Reason for enhancement When using git svn instead of svn to checkout the source the SVN revision number is recognized as "Unversioned directory" because it is not a SVN repository. The oscam version is then shown as "Unversioned directory". I made a patch which handles this case. Please add it to the source so one can use git svn without restrictions. Thanks.

= Possible impacts on other features I made checks so if something fails when getting the revision number from svn nothing is changed. So there should be no impact at all.