Translate common Ctrl-Left/Right/Delete/Backspace to the EMACS-style
sequences (i.e. Alt key based) for forward-word, backward-word, forwad-kill
and backward-kill. Requires MICROPY_REPL_EMACS_WORDS_MOVE to be defined so
the readline implementation interprets these.
This enables going back to previous wrapped lines using backspace or left
arrow: instead of just sticking to the beginning of a line, the cursor will
move a line up.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
