touchpad: ignore modifier key combos for dwt

touchpad: ignore modifier key combos for dwt

Inspired by the syndaemon -K switch and Anton Lindqvist's patch.
https://patchwork.freedesktop.org/patch/102417/

We already ignored modifiers for dwt. Now we also ignore modifier + key
combinations, i.e. hitting Ctrl+s to save does not trigger dwt, the touchpad
remains immediately usable.

However, if dwt is already active and a modifier combination is pressed, dwt
remains active, i.e. while typing, a shift + key does not disable dwt.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>