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/filebrowser/juce_FilePreviewComponent.h

@@ -0,0 +1,67 @@
+/*
+  ==============================================================================
+
+   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
+{
+
+//==============================================================================
+/**
+    Base class for components that live inside a file chooser dialog box and
+    show previews of the files that get selected.
+
+    One of these allows special extra information to be displayed for files
+    in a dialog box as the user selects them. Each time the current file or
+    directory is changed, the selectedFileChanged() method will be called
+    to allow it to update itself appropriately.
+
+    @see FileChooser, ImagePreviewComponent
+
+    @tags{GUI}
+*/
+class JUCE_API  FilePreviewComponent  : public Component
+{
+public:
+    //==============================================================================
+    /** Creates a FilePreviewComponent. */
+    FilePreviewComponent();
+
+    /** Destructor. */
+    ~FilePreviewComponent();
+
+    /** Called to indicate that the user's currently selected file has changed.
+
+        @param newSelectedFile  the newly selected file or directory, which may be
+                                a defualt File() object if none is selected.
+    */
+    virtual void selectedFileChanged (const File& newSelectedFile) = 0;
+
+
+private:
+    //==============================================================================
+    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (FilePreviewComponent)
+};
+
+} // namespace juce