get new version from: http://packages.qa.debian.org/m/mpack.html
 mpack_1.6.orig.tar.gz   ---> tar -xzf ---> mpack-1.6/
 mpack_1.6-4.diff.gz
 mpack_1.6-4.dsc 

and apply patch 'mpack_1.6-4.diff' to original dir: mpack-1.6/
> cd mpack-1.6
> patch < ../mpack_1.6-4.diff
patching file unixpk.c
patching file encode.c
patching file codes.c
patching file magic.c
patching file unixos.c
patching file xmalloc.c
patching file unixunpk.c
patching file decode.c
patching file uudecode.c
patching file part.c
patching file md5.h
patching file README.unix
patching file mkreadme.pl
patching file unixpk.man
patching file unixunpk.man
patching file watch
patching file changelog
patching file control
> cd .. ; mv mpack-1.6 mpack-1.6-4