stop readline from overwriting LINES

Basically that line lets nnn retain the WINCH signal for itself.

Looked up GNU readline library's repo and looked
for the first occurance of rl_change_environment.

The problem was that readline would completely block LINES from updating
after prompting the user. I'm not entirely sure why this happened, but
at least this patch fixes the problem.

2 changes:
- Toggle nav-as-you-type with left single/double click below last entry
- Handle mouse events when filter is on

Visit parent is now left single click outside context nums on top row.

This is limited to libncurses support of full mouse scrolling.
Ref: https://invisible-island.net/ncurses/man/curs_mouse.3x.html#h3-Mouse-events

Find a parent when CWD disappears

incase the user just lost access, it would be better to remember the
selected directory to keep it highlighted.

The previous behaviour would exit nnn when the CWD disappeared.

Add forgotten export for quitcd scripts

Fix quitcd snippets for 'zsh' and 'bash'

This reverts commit afdfcecb9c.