This adds support for very long input lines to still display the
input preview correct.

Add a reverse search that works similar to the ZSH one. It is
triggered with <ctrl> + r and <ctrl> + s. It skips duplicated history
entries and works with multiline statements. Matching entries indicate
the search parameter with an underscore and cancelling with <ctrl> + c
or escape brings back the original line.
Multiple matches in a single history entry work as well and are
matched in the order of the current search direction. The cursor is
positioned at the current match position of the history entry.
Changing the direction immediately searches checks for the next entry
in the expected direction from the current position on.
Entries are accepted as soon any button is pressed that doesn't
correspond with the reverse search.
The behavior is deactivated for simple terminals. They do not support
most ANSI escape codes that are necessary for this feature.

This just removes some redundant work and some other small things.

The cursor move functions accept a callback. It was possible that
`undefined` was returned in case there was no error instead of null.