[packages/ctorrent] allow negative integers ... should fix random "error, initial meta info failed"

taken from this bugreport:
http://sourceforge.net/tracker/?func=detail&aid=3159066&group_id=202532&atid=981959

thanks Norbert Zagyi <znorbi@znorbi.net> for the hint


git-svn-id: svn://svn.openwrt.org/openwrt/packages@35041 3c298f89-4303-0410-b956-a3cf2f4a3e73