`KeyAddrEventQueue::remove()` fails to confirm that the current queue is empty
before decrementing the length and shifting entries in the queue arrays. If
`remove()` or `shift()` is called when the queue is empty, `length_` gets
decremented from 0 to 255 (because it's unsigned), and then a large section of
memory gets shifted, mostly out of bounds of the event queue arrays, and
probably wreaking havoc with any number of things.
The plugin in this testcase should trigger this bug, and is detectable because
it affects the value for the current time. It's not guaranteed to detect this
bug, but it seems to be fairly consistent.
Signed-off-by: Michael Richters <gedankenexperimenter@gmail.com>