upgrade to JUCE 5.4.3. Remove (probably) unused JUCE modules. Remove VST2 target (it's been end-of-life'd by Steinberg and by JUCE)

modules/juce_audio_plugin_client/VST/juce_VSTCallbackHandler.h

@@ -27,14 +27,14 @@
 namespace juce
 {
 
-/** An interface to allow an AudioProcessor to receive VST specific calls from
+/** An interface to allow an AudioProcessor to send and receive VST specific calls from
     the host.
 
     @tags{Audio}
 */
 struct VSTCallbackHandler
 {
-    virtual ~VSTCallbackHandler() {}
+    virtual ~VSTCallbackHandler() = default;
 
     /** This is called by the VST plug-in wrapper when it receives unhandled
         plug-in "can do" calls from the host.
@@ -55,6 +55,22 @@ struct VSTCallbackHandler
                                                              pointer_sized_int value,
                                                              void* ptr,
                                                              float opt) = 0;
+
+    // Note: VS2013 prevents a "using" declaration here
+    /** The host callback function type. */
+    typedef pointer_sized_int (VstHostCallbackType) (int32 opcode,
+                                                     int32 index,
+                                                     pointer_sized_int value,
+                                                     void* ptr,
+                                                     float opt);
+
+    /** This is called once by the VST plug-in wrapper after its constructor.
+        You can use the supplied function to query the VST host.
+    */
+    virtual void handleVstHostCallbackAvailable (std::function<VstHostCallbackType>&& callback)
+    {
+        ignoreUnused (callback);
+    }
 };
 
 } // namespace juce