According to documentation and the comment blurb at start of default
sshcontrol, it should be possible to set per-key TTL for SSH keys (in the
sshcontrol file). This is however not, um, quite implemented. I am attaching a
patch to fix that. It's pretty trivial. The code I have added to parse the TTL
is a little silly and maybe wrong, but it happens to work for me. Ah, and, the
hexdigitp (...) is there because I didn't see a digitp (...) and isdigit from
ctype.h didn't occur to me (or maybe one can't use ctype for portability
reasons? whatever). Anyway, review (and eventual inclusion) would appreciated.