When a shift is not pressed, press it when a TopsyTurvy key is pressed, and keep
it down as long as the TopsyTurvy key is held, too. Release it when the key
toggles off. This fixes the jitter of #1 in the case where the key is pressed
without a modifier.
In the other case, when a TopsyTurvy key is pressed while a Shift is active too,
send a report after releasing the shifts, to make sure we do not jitter here,
either.
Fixes#1.
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>