document fringe-ignore-offset

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

change fringe defaults: always enabled and ~ as prefix

setup a fringe in the provided themes

tweak the about:new page

sync changelog

add fringe prefix and allow to override offset for fringes alone

sync changelog

document the `line.fringe' style identifier

add vi-like `~' fringes after the end of the buffers

meeeeuhteuhethuet

kill old, unused forward prototype for non-existant struct page

modeline: add an extra - after the trust status char 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.

specify that --help and --version also exit

remove the description about the session file format 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.