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_core/logging/juce_Logger.h

@@ -0,0 +1,91 @@
+/*
+  ==============================================================================
+
+   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
+{
+
+//==============================================================================
+/**
+    Acts as an application-wide logging class.
+
+    A subclass of Logger can be created and passed into the Logger::setCurrentLogger
+    method and this will then be used by all calls to writeToLog.
+
+    The logger class also contains methods for writing messages to the debugger's
+    output stream.
+
+    @see FileLogger
+
+    @tags{Core}
+*/
+class JUCE_API  Logger
+{
+public:
+    //==============================================================================
+    /** Destructor. */
+    virtual ~Logger();
+
+    //==============================================================================
+    /** Sets the current logging class to use.
+
+        Note that the object passed in will not be owned or deleted by the logger, so
+        the caller must make sure that it is not deleted while still being used.
+        A null pointer can be passed-in to reset the system to the default logger.
+    */
+    static void JUCE_CALLTYPE setCurrentLogger (Logger* newLogger) noexcept;
+
+    /** Returns the current logger, or nullptr if no custom logger has been set. */
+    static Logger* JUCE_CALLTYPE getCurrentLogger() noexcept;
+
+    /** Writes a string to the current logger.
+
+        This will pass the string to the logger's logMessage() method if a logger
+        has been set.
+
+        @see logMessage
+    */
+    static void JUCE_CALLTYPE writeToLog (const String& message);
+
+
+    //==============================================================================
+    /** Writes a message to the standard error stream.
+
+        This can be called directly, or by using the DBG() macro in
+        juce_PlatformDefs.h (which will avoid calling the method in non-debug builds).
+    */
+    static void JUCE_CALLTYPE outputDebugString (const String& text);
+
+
+protected:
+    //==============================================================================
+    Logger();
+
+    /** This is overloaded by subclasses to implement custom logging behaviour.
+        @see setCurrentLogger
+    */
+    virtual void logMessage (const String& message) = 0;
+
+private:
+    static Logger* currentLogger;
+};
+
+} // namespace juce