Start moving towards C++ only UI code. Assume C++ for the replay API

* The C# P/Invoke stuff doesn't directly use the header, and we are soon
  going to deprecate the C interface entirely.

renderdoccmd/renderdoccmd_apple.cpp

@@ -35,7 +35,7 @@ void Daemonise()
 {
 }
 
-void DisplayRendererPreview(ReplayRenderer *renderer, TextureDisplay &displayCfg, uint32_t width,
+void DisplayRendererPreview(IReplayRenderer *renderer, TextureDisplay &displayCfg, uint32_t width,
                             uint32_t height)
 {
 }