Fix non-standard-conform init of std::atomic_flag with true

Author: sgretscher

PlugIn/ARAPlug.cpp

@@ -910,6 +910,8 @@ DocumentController::DocumentController (const PlugInEntry* entry, const ARADocum
   _hostModelUpdateController { instance },
   _hostPlaybackController { instance }
 {
+    _analysisProgressIsSynced.test_and_set (std::memory_order_release);
+
 #if ARA_VALIDATE_API_CALLS
     _documentControllers.emplace (this, entry);
 #endif

PlugIn/ARAPlug.h

@@ -1335,7 +1335,7 @@ class DocumentController : public DocumentControllerInterface,
     std::map<AudioSource*, ContentUpdateScopes> _audioSourceContentUpdates;
     std::map<AudioModification*, ContentUpdateScopes> _audioModificationContentUpdates;
     std::map<PlaybackRegion*, ContentUpdateScopes> _playbackRegionContentUpdates;
-    std::atomic_flag _analysisProgressIsSynced { true };
+    std::atomic_flag _analysisProgressIsSynced/* { true } C++ standard only allows for default-init to false */;
 
     bool _isHostEditingDocument { false };