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_gui_basics/widgets/juce_ToolbarItemPalette.h

@@ -0,0 +1,78 @@
+/*
+  ==============================================================================
+
+   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 component containing a list of toolbar items, which the user can drag onto
+    a toolbar to add them.
+
+    You can use this class directly, but it's a lot easier to call Toolbar::showCustomisationDialog(),
+    which automatically shows one of these in a dialog box with lots of extra controls.
+
+    @see Toolbar
+
+    @tags{GUI}
+*/
+class JUCE_API  ToolbarItemPalette    : public Component,
+                                        public DragAndDropContainer
+{
+public:
+    //==============================================================================
+    /** Creates a palette of items for a given factory, with the aim of adding them
+        to the specified toolbar.
+
+        The ToolbarItemFactory::getAllToolbarItemIds() method is used to create the
+        set of items that are shown in this palette.
+
+        The toolbar and factory must not be deleted while this object exists.
+    */
+    ToolbarItemPalette (ToolbarItemFactory& factory,
+                        Toolbar& toolbar);
+
+    /** Destructor. */
+    ~ToolbarItemPalette();
+
+    //==============================================================================
+    /** @internal */
+    void resized() override;
+
+private:
+    ToolbarItemFactory& factory;
+    Toolbar& toolbar;
+    Viewport viewport;
+    OwnedArray<ToolbarItemComponent> items;
+
+    friend class Toolbar;
+    void replaceComponent (ToolbarItemComponent&);
+    void addComponent (int itemId, int index);
+
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ToolbarItemPalette)
+};
+
+} // namespace juce