This introduces the setting single_instance_per_file and
the command line flag --single-instance.

With this option and background_color_fullscreen you can freely configure the color of your liking.

Default key binding: F9

Allow user to manually add entries to the jump list. Similar to m in
vim.

This is useful for reading documents that have a cover page in a book layout.

Every time a jump occurs its origin is saved. You can then move through
those saved positions, e.g. to return to the table of contents after
having read a section.

Configure via background_opacity setting. Always draws fully opaque when
in fullscreen.

The command line options right before each file will be used
individually.

auto_* removed, every action now has a fallback for layouts that don't
support smooth scrolling.
Half and full screen scrolling added.

Currently supported options are:
	- page NUM
	- fullscreen
	- help

For now build with 'a2x -f manpage katarakt.txt'
Proper build target coming soon