This terminal subsystem is attempt to finally reorganize the original
not-much-touched lowlevel/terminal.* and lowlevel/kbd.* (terminal.c and kbd.c
in the original Links tree) in a sane manner.

It is still work in progress (design-wise!). It should be stable, but it needs
structural (not necessarily functional) reorganization. Some process is
started, but a lot of work remains to be done.


Functions need to be renamed to match some uniform pattern.

The existing files need to be further split (at least some of them), many
symbols need to be moved around to their proper location.

A lot of the symbols don't belong to the terminal subsystem at all.

More object-like structure needs to be deployed.

I'm not yet sure how to support graphics, ncurses etc backends yet. Some of
this code is universal, some if it is textmode-specific, some of it is direct
implementation of our I/O. More structure inside of this directory is expected
to appear later when needed.