kconfig:
 * use git_archive method to download kconfig sources, the old method didn't work anymore (s. [http://www.ip-phone-forum.de/showthread.php?t=257466 this thread] for details)
 * correct kconfig version (the proper one is some pre-3.8-git)
 * add git to the list of build dependencies


git-svn-id: file:///var/svn/freetz/trunk@10216 149334a1-2f27-0410-a3b9-fc62619ac1e6