This reverts commit b85b67c2f0.
The Ctrl key was too hard to use in the new position, especially in
combination with arrows or backspace.
Leave the switching key in the numeric layout however, where the Ctrl
key is not very useful. Put Ctrl on the top-right because bottom-right
is where the switching key is in the other layouts.
Allow specifying a layout for programming and add a key for switching to
it easily.
The switching key is placed on the top edge of the space bar.
The option has no effect by default because the ergonomic isn't ideal,
it needs to be enabled explicitly.
Users of Latin-script languages certainly prefer to use one layout (for
programming or not). This feature might be removed in favor of a better
language-switching mechanisms in the future.
