Split the tsig-keygen/ddns-confgen man page into two separate documents
ddns-confgen are effectively the same binary,
their command line parameters are rather different and half of them are
ddns-confgen. The user does not need to be aware that the
same binary is used "behind the scenes" for two tools serving quite
different purposes - and keeping a combined man page around causes
headaches while also not giving us many benefits.
Given the above, it seems sensible to have two separate man pages for