ACARS 3.0.0-nightly.504

Added

• (release) Mac client!
• (release) Linux client!
• (release) Ship the X-Plane plugins on mac and linux

Fixed

• (export) Round-trip queue row ids
• (sim) Atomic CTS swap on stop and dispose
• (airports) Resolve LID and briefing aliases
• (session) Stop per-session state leaking forward
• (db) Checkpoint behind the write lock, with backoff
• (map) Clamp DEM lat, globe ease, log dedupe
• (webui) Keep planning page until start succeeds
• (xplane) Find airports by any known ident
• (xplane) Define _XOPEN_SOURCE for CrashHandler on macOS
• (linux) Make the AppImage actually run