Provide a script to regenerate the Blowfish init tables.

Since I've recently published a program that can easily generate the
required digits of pi, and since I was messing around in sshblowf.c
already, it seemed like a good idea to provide a derivation of all
that hex data.

(cherry picked from commit 2968563180ae5013976123d8c5106a6c394b96a6)