fix macOS build (following Projucer changes made in Windows, which removed /Applications/JUCE/modules from its headers). move JUCE headers under source control, so that Windows and macOS can both build against same version of JUCE. remove AUv3 target (I think it's an iOS thing, so it will never work with this macOS fluidsynth dylib).

modules/juce_events/broadcasters/juce_AsyncUpdater.h

@@ -0,0 +1,110 @@
+/*
+  ==============================================================================
+
+   This file is part of the JUCE library.
+   Copyright (c) 2017 - ROLI Ltd.
+
+   JUCE is an open source library subject to commercial or open-source
+   licensing.
+
+   The code included in this file is provided under the terms of the ISC license
+   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
+   To use, copy, modify, and/or distribute this software for any purpose with or
+   without fee is hereby granted provided that the above copyright notice and
+   this permission notice appear in all copies.
+
+   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
+   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
+   DISCLAIMED.
+
+  ==============================================================================
+*/
+
+namespace juce
+{
+
+//==============================================================================
+/**
+    Has a callback method that is triggered asynchronously.
+
+    This object allows an asynchronous callback function to be triggered, for
+    tasks such as coalescing multiple updates into a single callback later on.
+
+    Basically, one or more calls to the triggerAsyncUpdate() will result in the
+    message thread calling handleAsyncUpdate() as soon as it can.
+
+    @tags{Events}
+*/
+class JUCE_API  AsyncUpdater
+{
+public:
+    //==============================================================================
+    /** Creates an AsyncUpdater object. */
+    AsyncUpdater();
+
+    /** Destructor.
+        If there are any pending callbacks when the object is deleted, these are lost.
+    */
+    virtual ~AsyncUpdater();
+
+    //==============================================================================
+    /** Causes the callback to be triggered at a later time.
+
+        This method returns immediately, after which a callback to the
+        handleAsyncUpdate() method will be made by the message thread as
+        soon as possible.
+
+        If an update callback is already pending but hasn't happened yet, calling
+        this method will have no effect.
+
+        It's thread-safe to call this method from any thread, BUT beware of calling
+        it from a real-time (e.g. audio) thread, because it involves posting a message
+        to the system queue, which means it may block (and in general will do on
+        most OSes).
+    */
+    void triggerAsyncUpdate();
+
+    /** This will stop any pending updates from happening.
+
+        If called after triggerAsyncUpdate() and before the handleAsyncUpdate()
+        callback happens, this will cancel the handleAsyncUpdate() callback.
+
+        Note that this method simply cancels the next callback - if a callback is already
+        in progress on a different thread, this won't block until the callback finishes, so
+        there's no guarantee that the callback isn't still running when the method returns.
+    */
+    void cancelPendingUpdate() noexcept;
+
+    /** If an update has been triggered and is pending, this will invoke it
+        synchronously.
+
+        Use this as a kind of "flush" operation - if an update is pending, the
+        handleAsyncUpdate() method will be called immediately; if no update is
+        pending, then nothing will be done.
+
+        Because this may invoke the callback, this method must only be called on
+        the main event thread.
+    */
+    void handleUpdateNowIfNeeded();
+
+    /** Returns true if there's an update callback in the pipeline. */
+    bool isUpdatePending() const noexcept;
+
+    //==============================================================================
+    /** Called back to do whatever your class needs to do.
+
+        This method is called by the message thread at the next convenient time
+        after the triggerAsyncUpdate() method has been called.
+    */
+    virtual void handleAsyncUpdate() = 0;
+
+private:
+    //==============================================================================
+    class AsyncUpdaterMessage;
+    friend class ReferenceCountedObjectPtr<AsyncUpdaterMessage>;
+    ReferenceCountedObjectPtr<AsyncUpdaterMessage> activeMessage;
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AsyncUpdater)
+};
+
+} // namespace juce