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_opengl/opengl/juce_OpenGLRenderer.h

@@ -0,0 +1,82 @@
+/*
+  ==============================================================================
+
+   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.
+
+   By using JUCE, you agree to the terms of both the JUCE 5 End-User License
+   Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
+   27th April 2017).
+
+   End User License Agreement: www.juce.com/juce-5-licence
+   Privacy Policy: www.juce.com/juce-5-privacy-policy
+
+   Or: You may also use this code under the terms of the GPL v3 (see
+   www.gnu.org/licenses).
+
+   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
+{
+
+//==============================================================================
+/**
+    A base class that should be implemented by classes which want to render openGL
+    on a background thread.
+
+    @see OpenGLContext
+
+    @tags{OpenGL}
+*/
+class JUCE_API  OpenGLRenderer
+{
+public:
+    OpenGLRenderer() {}
+    virtual ~OpenGLRenderer() {}
+
+    /** Called when a new GL context has been created.
+        You can use this as an opportunity to create your textures, shaders, etc.
+        When the method is invoked, the new GL context will be active.
+        Note that this callback will be made on a background thread, so make sure
+        that your implementation is thread-safe.
+    */
+    virtual void newOpenGLContextCreated() = 0;
+
+    /** Called when you should render the next openGL frame.
+
+        Note that this callback will be made on a background thread.
+
+        If the context is attached to a component in order to do component rendering,
+        then the MessageManager will be locked when this callback is made.
+
+        If no component rendering is being done, then the MessageManager will not be
+        locked, and you'll need to make sure your code is thread-safe in any
+        interactions it has with your GUI classes.
+
+        For information about how to trigger a render callback, see
+        OpenGLContext::triggerRepaint() and OpenGLContext::setContinuousRepainting().
+    */
+    virtual void renderOpenGL() = 0;
+
+    /** Called when the current openGL context is about to close.
+        You can use this opportunity to release any GL resources that you may have
+        created.
+
+        Note that this callback will be made on a background thread, so make sure
+        that your implementation is thread-safe.
+
+        (Also note that on Android, this callback won't happen, because there's currently
+        no way to implement it..)
+    */
+    virtual void openGLContextClosing() = 0;
+};
+
+} // namespace juce