Prepare version 0.2.10.5
Be brutal in overcoming the problem of pretty-show-1.6.2 vs old 'happy'

The goal is to have the package installable from hackage just
via "cabal install" even if 'happy' is oldish (such as on travis)
and pretty-show is not installed. When the most common GHC comes
with a new 'happy', this constraint can be lifted.