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_events/native/juce_linux_EventLoop.h

@@ -0,0 +1,55 @@
+/*
+  ==============================================================================
+
+   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
+{
+
+namespace LinuxEventLoop
+{
+    struct CallbackFunctionBase
+    {
+        virtual ~CallbackFunctionBase() {}
+        virtual bool operator()(int fd) = 0;
+        bool active = true;
+    };
+
+    template <typename FdCallbackFunction>
+    struct CallbackFunction : public CallbackFunctionBase
+    {
+        FdCallbackFunction callback;
+
+        CallbackFunction (FdCallbackFunction c) : callback (c) {}
+
+        bool operator() (int fd) override { return callback (fd); }
+    };
+
+    template <typename FdCallbackFunction>
+    void setWindowSystemFd (int fd, FdCallbackFunction readCallback)
+    {
+        setWindowSystemFdInternal (fd, new CallbackFunction<FdCallbackFunction> (readCallback));
+    }
+    void removeWindowSystemFd() noexcept;
+
+    void setWindowSystemFdInternal (int fd, CallbackFunctionBase* readCallback) noexcept;
+}
+
+} // namespace juce