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_core/threads/juce_TimeSliceThread.h

@@ -0,0 +1,150 @@
+/*
+  ==============================================================================
+
+   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
+{
+
+class TimeSliceThread;
+
+
+//==============================================================================
+/**
+    Used by the TimeSliceThread class.
+
+    To register your class with a TimeSliceThread, derive from this class and
+    use the TimeSliceThread::addTimeSliceClient() method to add it to the list.
+
+    Make sure you always call TimeSliceThread::removeTimeSliceClient() before
+    deleting your client!
+
+    @see TimeSliceThread
+
+    @tags{Core}
+*/
+class JUCE_API  TimeSliceClient
+{
+public:
+    /** Destructor. */
+    virtual ~TimeSliceClient()   {}
+
+    /** Called back by a TimeSliceThread.
+
+        When you register this class with it, a TimeSliceThread will repeatedly call
+        this method.
+
+        The implementation of this method should use its time-slice to do something that's
+        quick - never block for longer than absolutely necessary.
+
+        @returns    Your method should return the number of milliseconds which it would like to wait before being called
+                    again. Returning 0 will make the thread call again as soon as possible (after possibly servicing
+                    other busy clients). If you return a value below zero, your client will be removed from the list of clients,
+                    and won't be called again. The value you specify isn't a guaranteee, and is only used as a hint by the
+                    thread - the actual time before the next callback may be more or less than specified.
+                    You can force the TimeSliceThread to wake up and poll again immediately by calling its notify() method.
+    */
+    virtual int useTimeSlice() = 0;
+
+
+private:
+    friend class TimeSliceThread;
+    Time nextCallTime;
+};
+
+
+//==============================================================================
+/**
+    A thread that keeps a list of clients, and calls each one in turn, giving them
+    all a chance to run some sort of short task.
+
+    @see TimeSliceClient, Thread
+
+    @tags{Core}
+*/
+class JUCE_API  TimeSliceThread   : public Thread
+{
+public:
+    //==============================================================================
+    /**
+        Creates a TimeSliceThread.
+
+        When first created, the thread is not running. Use the startThread()
+        method to start it.
+    */
+    explicit TimeSliceThread (const String& threadName);
+
+    /** Destructor.
+
+        Deleting a Thread object that is running will only give the thread a
+        brief opportunity to stop itself cleanly, so it's recommended that you
+        should always call stopThread() with a decent timeout before deleting,
+        to avoid the thread being forcibly killed (which is a Bad Thing).
+    */
+    ~TimeSliceThread();
+
+    //==============================================================================
+    /** Adds a client to the list.
+        The client's callbacks will start after the number of milliseconds specified
+        by millisecondsBeforeStarting (and this may happen before this method has returned).
+    */
+    void addTimeSliceClient (TimeSliceClient* clientToAdd, int millisecondsBeforeStarting = 0);
+
+    /** If the given client is waiting in the queue, it will be moved to the front
+        and given a time-slice as soon as possible.
+        If the specified client has not been added, nothing will happen.
+    */
+    void moveToFrontOfQueue (TimeSliceClient* clientToMove);
+
+    /** Removes a client from the list.
+        This method will make sure that all callbacks to the client have completely
+        finished before the method returns.
+    */
+    void removeTimeSliceClient (TimeSliceClient* clientToRemove);
+
+    /** Removes all the active and pending clients from the list.
+        This method will make sure that all callbacks to clients have finished before the
+        method returns.
+    */
+    void removeAllClients();
+
+    /** Returns the number of registered clients. */
+    int getNumClients() const;
+
+    /** Returns one of the registered clients. */
+    TimeSliceClient* getClient (int index) const;
+
+    //==============================================================================
+   #ifndef DOXYGEN
+    void run() override;
+   #endif
+
+    //==============================================================================
+private:
+    CriticalSection callbackLock, listLock;
+    Array<TimeSliceClient*> clients;
+    TimeSliceClient* clientBeingCalled = nullptr;
+
+    TimeSliceClient* getNextClient (int index) const;
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (TimeSliceThread)
+};
+
+} // namespace juce