binary diff and patch using the BSDIFF4-format

The code is mostly derived from cx_bsdiff (written by Anthony
Tuininga, http://cx-bsdiff.sourceforge.net/). The cx_bsdiff code in
turn was derived from bsdiff, the standalone utility produced for BSD
which can be found at http://www.daemonology.net/bsdiff. In addition
to the two functions (diff and patch) cx_bsdiff provides, this package
includes:

an interface to the BSDIFF4-format

command line interfaces: bsdiff4 and bspatch4