getch2: Deactivate getch2 on SIGINT; also handle SIGQUIT
getch2: Load the "ce", "ks" and "ke" caps into a static buffer

Fixes reports of printing of garbage (or anything else) other than clearing
the status line to the end of line: the buffer returned by termcap_get
could get moved, and if that happened then these 3 caps pointed to garbage.