Physical movement and other events on some newer computers are no longer treated as inappropriate key presses. Previously, this silenced speech and sometimes triggered NVDA commands.
Some devices notify about these events using non-standard scan codes, for which GetKeyNameText returns inappropriate names. These report a vk code of 0xFF, so handle this appropriately.
These will now report as unknown in input help mode and can be mapped as gestures if desired using the log.
Re #3468.