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_dsp/processors/juce_ProcessorWrapper.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
+{
+namespace dsp
+{
+
+/**
+    Acts as a polymorphic base class for processors.
+    This exposes the same set of methods that a processor must implement as virtual
+    methods, so that you can use the ProcessorWrapper class to wrap an instance of
+    a subclass, and then pass that around using ProcessorBase as a base class.
+    @see ProcessorWrapper
+
+    @tags{DSP}
+*/
+struct ProcessorBase
+{
+    ProcessorBase() = default;
+    virtual ~ProcessorBase() = default;
+
+    virtual void prepare (const ProcessSpec&)  = 0;
+    virtual void process (const ProcessContextReplacing<float>&) = 0;
+    virtual void reset() = 0;
+};
+
+
+//==============================================================================
+/**
+    Wraps an instance of a given processor class, and exposes it through the
+    ProcessorBase interface.
+    @see ProcessorBase
+
+    @tags{DSP}
+*/
+template <typename ProcessorType>
+struct ProcessorWrapper  : public ProcessorBase
+{
+    void prepare (const ProcessSpec& spec) override
+    {
+        processor.prepare (spec);
+    }
+
+    void process (const ProcessContextReplacing<float>& context) override
+    {
+        processor.process (context);
+    }
+
+    void reset() override
+    {
+        processor.reset();
+    }
+
+    ProcessorType processor;
+};
+
+} // namespace dsp
+} // namespace juce