PDP 8E Simulator for Mac

This is the 25th anniversary of the PDP-8/E Simulator, and version 2.2 contains the following improvements:

• The PDP-8/E Simulator now has a Real Time Clock plug-in with various clock models and frequencies
• Improved real time performance (finally without any busy waiting) enables the simulator to pass the MAINDEC-8E-D8AC-PB DK8-E Clocks Diagnostics for all clock frequencies
• An improved plug-in API enables plug-ins to be written in Swift
• A Swift version of the Memory Content demo plug-in was added
• For the RK05 disk drives, now a gauge indicates the last accessed track of the disk and the kind of access (Read, Write or Seek)
• The ASR-33 no longer replaces "--" with "-" when "Use smart quotes and dashes" is enabled in the "Keyboard" System Preferences
• Fixed a very rare situation that could cause two PDP-8/E run threads to run simultaneously, causing total confusion
• Many minor bugs fixed, including typographic errors and visual glitches with Dark Mode
• Improved compatibility with macOS 10.14 "Mojave" and macOS 10.15 "Catalina"