Add %L format code (temporary copy of filelist)

Not sure if it protects against many spambots. Can't hurt, anyways.

update AUTHORS to obscure some email

[OT: wow, feh is back after all these years! way to go!]

i am proposing to obscure all these emails, because today, putting emails in plain text is just inviting spam.

i would do the same for the rest, but i did not want to over-reach. if you agree, i will happily do it.

New sort option: mtime

Sort filelist by modification time, newer files first. Useful for
perusing a directory of images by most recently added or changed.

Patch by sdaau on IRC. Thanks!