Build needs to link against a termcap library on some systems

[next-mad-hatter]

Currently out of the box build fails on some systems (e.g. latest Slackware Linux).

From what I gather [1] the readline library might not be explicitly linked to one providing termcap capabilities, so it needs to be explicitly given to the linker. On Slackware either --link-flags "-lncurses" or --link-flags "-ltermcap" works.

Not sure though if automatic detection, settling for one of the two libs or just a mention in the documentation would be preferred solution.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=499837