termcap has last been updated in 2002, and is relying on a lot of
deprecated C99 behavior. All two current users are fine without it,
so just remove it completely.
- Update imgcat to 2.5.1 to get rid of prebuilt object files that have
accidentally been included in the previous release tarball.
- Add a missing dependency on `termcap`.
- Remove an unused include of `err.h`, which we do not support.
- Use actually working settings for installing the built files.
We may need entries with spaces in makeopts, installopts, and
configopts, and at that point we should also convert depends and
auth_opts to avoid confusion.
