print_vline can handle a NULL .line, so I can avoid the long comment and the ugly cast.

in part for symmetry, and in part because it seems a good spot to add an indicator for the presence of a client certificate in the future.

It's been changed recently (see history & killed files) and I don't want to keep documenting it: users shouldn't mess with their history file that easily (this is not an excuse for sloppy parsing, which isn't the case.) Furthermore, the format is easy, I think intuitive, and the code easily found in fs.c.