SDL Sopwith v2.4.0

• There is now an emscripten (web) version, available on the website.
  (Thanks go to @midzer, who previously did an Emscripten port and whose
  work I built on to put the build script together).
• It is now possible to make and load custom levels (there is no proper
  level editor available yet though).
• There are now a number of alternative palettes that can be used that
  simulate different CGA palettes and old monitors (thanks techknight).
• There are now hotkeys to end or restart the current game (thanks
  techknight).
• There is now a -p command line option to specify TCP port number.
• The Windows package now includes a copy of the Unix manual pages.
• Sound is now oversampled to reduce sound aliasing (thanks @kmill).
• Starting level is now synchronized between players at multiplayer start.
• A bug was fixed with the keybindings menu not working (thanks ranguli,
  NY00123)
• A missing include was added to fix build on Alpine Linux (thanks John
  Gebbie)
• An input bug was fixed where a backspace would leave some visual
  corruption, and the cursor now blinks.
• A bug was fixed where the same medal could be awarded twice.
• Timing of music on the title screen was fixed (thanks @NY00123).