change the ipkg cookie as discussed in #FreeWRT but move it to bin/packages/.stamps/ so that the usual and already existing cleaning methods will get it in all cases and no manual post-processing would be needed
THIS CHANGE REQUIRES A “make clean”!
git-svn-id: svn://www.freewrt.org/trunk/freewrt@2654 afb5a338-a214-0410-bd46-81f09a774fd1