This is an improvement on retro-tap, solving the 'flashing hold' issue
users people experience.
When the tapping-term expires, the hold key is normally pressed. When
retro-tap is enabled, this is undesirable; only an interrupted hold-tap
should trigger the hold behavior.
This change disables the hold behavior for the 'STATUS_HOLD_TIMER'
state when retro-tap is enabled, and makes sure the
'STATUS_HOLD_INTERRUPT' state will be triggered when appropriate.
