The termcap entry for "xterm" defaults to some x11r5-like xterm.

However, we've been shipping x11r6 xterms for a while, and the x11r5
description makes at least window(1) behave badly.

I have just appended explanations to PR bin/15667.

Any idea of a correct fix?
(or: "can someone please update termcap.src if you feel confident
      enough about which local changes we need to keep?")

thanks,
 Aymeric