This patch adds the handling of 'CHARACTER' events as emitted by the
input-filter's character generator (<chargen>). To avoid interpreting
press/release events twice (at the input filter and by the terminal's
built-in scancode tracker), the terminal's scancode tracker can be
explicitly disabled via <config> <keyboard layout="none"/> </config>.
In the future, the terminal's built-in scancode tracker will be
removed.
The use of the terminal with the input filter is illustrated by the
'terminal_echo.run' script.
Issue #2264
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
