vm-superio-v0.2.0

Added

• Added emulation support for an i8042 controller that only handles the CPU
  reset (#11).
• Added SerialEvents trait, which can be implemented by a backend that wants
  to keep track of serial events using metrics, logs etc
  (#5).
• Added a threat model to the serial console documentation
  (#16).
• Added emulation support for an ARM PL031 Real Time Clock
  (#22), and the RTCEvents
  trait, used for keeping track of RTC events
  (#34).
• Added an implementation for Arc<EV> for both serial console and RTC device
  (#40).
• Added methods for retrieving a reference to the events object for both serial
  console and RTC device
  (#40).

Changed

• Changed the notification mechanism from EventFd to the Trigger abstraction
  for both serial console and i8042
  (#7).

Fixed

• Limited the maximum number of bytes allowed at a time, when enqueuing input
  for serial, to 64 (FIFO_SIZE) to avoid memory pressure
  (#17).
• Fixed possible indefinite blocking of the serial driver by always sending the
  THR Empty interrupt to it when trying to write to the device
  (#23).