Version 3.1

• Use Java language level 16, so now Java 16 is required to run Run-REDUCE.jar.
• Delete the compatibility code to handle the obsolete REDUCE Versions preference.
• Improve display of warnings and errors.
• Improve handling of the Stop REDUCE menu item and explicit "bye" etc. commands to wait for REDUCE to stop. (However, note that killing REDUCE when run via a cmd shell on Microsoft Windows only kills the shell and leaves REDUCE running!)
• Add an Options menu with a check item Pop-up Queries. When this is selected, which it is by default, pop up a confirmation alert when REDUCE queries the user. Always strip any echoed y/Y/n/N after responding to a user query.
• Add a check item Show Menu History to the Options menu. When this is selected, which it is not by default, scrolling through previous input shows REDUCE commands generated by the menus. They are also shown if the Shift key is held down while scrolling through previous input.
• Save Options menu settings as preferences.
• Load Packages dialog:
  • Preserve _ characters in the display of package names. Remove inappropriate packages from the package list.
  • Right-click a package, or select one package and press the Display Manual Entry button, to display the manual entry (if it exists) for the package, using the default web browser.
  • Map REDLOG sub-packages to the REDLOG manual entry; exclude redfront.
• Write UserGuide.html to ~/Run-REDUCE_User_Guide.html, which the default web browser on Ubuntu 22 can open. This fixes issue #3.