Update `terminfo` to version 0.3.2.6

Thus GHC's in-tree version corresponds exactly to
[hackage:terminfo-0.3.2.6]. Morever, `terminfo` has moved
to GitHub as well (https://github.com/judah/terminfo) so
the upstream repo URL in `packages` is updated as well.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>