Note that this is (and always was) a terrible hack and we really should
replace it with something reasonable which wouldn't need changing every
time linuxdoc-tools evolve.

I also needed to include a patched version of LinuxDocTools.pm, because the
original one explicitly refused to work with a non-linuxdoc DTD. The authors
of linuxdoc recommend to use sgmltools-lite in such cases, but it would mean
rewritting our formatting rules to the DSSSL language which I don't dare to
speak about here :)

Work around that.

address. Need to do it better for the other neighbors -- the current
solution works only if they use the standard 64+64 global addresses
and the interface identifier in lower 64 bits is the same as for the
link-scope addresses.

and only the highest scope one has IA_PRIMARY set, so report
the remaining ones as "Unselected".

such case. Thanks to silvio@big.net.

with two exceptions:

   o  Any non-zero field width is automatically replaced by standard
      IP address width. This hides dependences on IPv4/IPv6.
   o  %#I generates hexadecimal form of the address.

Therefore |%I| generates unpadded format, |%1I| full size flush-right,
and |%-1I| full size flush-left format.