tichksum: replace with upward compatible rewrite
 * works on lillte endian and big endian
 * works on 32 bit and 64 bit
 * can add, verify and remove a checksum
 * default action is compatible with original tichksum


git-svn-id: file:///var/svn/freetz/trunk@12596 149334a1-2f27-0410-a3b9-fc62619ac1e6