Regenerate lookman index on install

[mmnmnnmnmm]

The indices in the repo have not been updated in 17 years.

I decided against pushing the updated indices themselves as the changeset is quite large.
Maybe they should just be removed and only generated on install?

   man/lookman.index | 10087 +++++++++++++++++++++++++++++++++++++++++++++++++++--
   man/man1/INDEX    |    11 +-
   man/man3/INDEX    |     2 +-
   3 files changed, 9804 insertions(+), 296 deletions(-)

This may not be the best way to do it, but it works fine for packaging in a distro.