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_data_structures/undomanager/juce_UndoableAction.h

@@ -0,0 +1,101 @@
+/*
+  ==============================================================================
+
+   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
+{
+
+//==============================================================================
+/**
+    Used by the UndoManager class to store an action which can be done
+    and undone.
+
+    @see UndoManager
+
+    @tags{DataStructures}
+*/
+class JUCE_API  UndoableAction
+{
+protected:
+    /** Creates an action. */
+    UndoableAction() noexcept   {}
+
+public:
+    /** Destructor. */
+    virtual ~UndoableAction()   {}
+
+    //==============================================================================
+    /** Overridden by a subclass to perform the action.
+
+        This method is called by the UndoManager, and shouldn't be used directly by
+        applications.
+
+        Be careful not to make any calls in a perform() method that could call
+        recursively back into the UndoManager::perform() method
+
+        @returns    true if the action could be performed.
+        @see UndoManager::perform
+    */
+    virtual bool perform() = 0;
+
+    /** Overridden by a subclass to undo the action.
+
+        This method is called by the UndoManager, and shouldn't be used directly by
+        applications.
+
+        Be careful not to make any calls in an undo() method that could call
+        recursively back into the UndoManager::perform() method
+
+        @returns    true if the action could be undone without any errors.
+        @see UndoManager::perform
+    */
+    virtual bool undo() = 0;
+
+    //==============================================================================
+    /** Returns a value to indicate how much memory this object takes up.
+
+        Because the UndoManager keeps a list of UndoableActions, this is used
+        to work out how much space each one will take up, so that the UndoManager
+        can work out how many to keep.
+
+        The default value returned here is 10 - units are arbitrary and
+        don't have to be accurate.
+
+        @see UndoManager::getNumberOfUnitsTakenUpByStoredCommands,
+             UndoManager::setMaxNumberOfStoredUnits
+    */
+    virtual int getSizeInUnits()    { return 10; }
+
+    /** Allows multiple actions to be coalesced into a single action object, to reduce storage space.
+
+        If possible, this method should create and return a single action that does the same job as
+        this one followed by the supplied action.
+
+        If it's not possible to merge the two actions, the method should return a nullptr.
+    */
+    virtual UndoableAction* createCoalescedAction (UndoableAction* nextAction)  { ignoreUnused (nextAction); return nullptr; }
+};
+
+} // namespace juce