Sdl backend (#670)

* [audio] added sdl audio backend and in-tree atrac9 decoder

* [input] replaced per-platform pad readers with sdl gamepad input

* [video] added sdl window and host display plumbing

* [gui] added host display options and per-game render settings

* [bink] synced host movie playback to the guest audio clock

* [cpu] hooked windows write faults into guest image tracking

* [perf] added guest and render profiling, reserved host cpu lanes

* [kernel] fixed stale pthread mutex handle alias

* [host] wired the sdl session, save-data paths and project references

* [audio] hoisted ajm trace stackalloc out of its loop

* [video] Add guest image sync setting

* [build] Strip native symbols

* reuse

src/SharpEmu.HLE/Host/IHostAudioStream.cs

@@ -15,4 +15,17 @@ public interface IHostAudioStream : IDisposable
     /// audio, in which case the caller paces the guest itself.
     /// </summary>
     bool Submit(ReadOnlySpan<byte> stereoPcm16);
+
+    /// <summary>
+    /// Audio already handed to the device and not yet played, in milliseconds —
+    /// the cushion protecting playback from a late submission. Zero means the
+    /// device has run dry and is emitting silence.
+    ///
+    /// Callers that pace the guest against an emulated hardware queue need this:
+    /// pacing purely on wall clock releases exactly one buffer per buffer-period
+    /// and so keeps the cushion at zero, which turns any scheduling jitter into
+    /// an audible dropout. Returns -1 when the backend cannot report a depth, in
+    /// which case callers must fall back to their own pacing.
+    /// </summary>
+    int QueuedMilliseconds => -1;
 }