Virtualize wxUIActionSimulator implementation

Extract platform-specific code in a wxUIActionSimulatorImpl-derived class
instead of keeping it in wxUIActionSimulator itself.

This will allow determining which implementation to use dynamically (i.e. at
run-time and not compile-time) to use later and already allows to get rid of
an __WXOSX__ #ifdef in common code.

include/wx/private/uiaction.h

@@ -0,0 +1,44 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/private/uiaction.h
+// Purpose:     wxUIActionSimulatorImpl declaration
+// Author:      Vadim Zeitlin
+// Created:     2016-05-21
+// Copyright:   (c) 2016 Vadim Zeitlin <vadim@wxwidgets.org>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_PRIVATE_UIACTION_H_
+#define _WX_PRIVATE_UIACTION_H_
+
+// ----------------------------------------------------------------------------
+// Platform-specific implementation of wxUIActionSimulator
+// ----------------------------------------------------------------------------
+
+class wxUIActionSimulatorImpl
+{
+public:
+    wxUIActionSimulatorImpl() { }
+    virtual ~wxUIActionSimulatorImpl() { }
+
+    // Low level mouse methods which must be implemented in the derived class.
+    virtual bool MouseMove(long x, long y) = 0;
+    virtual bool MouseDown(int button = wxMOUSE_BTN_LEFT) = 0;
+    virtual bool MouseUp(int button = wxMOUSE_BTN_LEFT) = 0;
+
+    // Higher level mouse methods which have default implementation in the base
+    // class but can be overridden if necessary.
+    virtual bool MouseClick(int button = wxMOUSE_BTN_LEFT);
+    virtual bool MouseDblClick(int button = wxMOUSE_BTN_LEFT);
+    virtual bool MouseDragDrop(long x1, long y1, long x2, long y2,
+                               int button = wxMOUSE_BTN_LEFT);
+
+    // The low-level port-specific function which really generates the key
+    // presses. It should generate exactly one key event with the given
+    // parameters.
+    virtual bool DoKey(int keycode, int modifiers, bool isDown) = 0;
+
+private:
+    wxDECLARE_NO_COPY_CLASS(wxUIActionSimulatorImpl);
+};
+
+#endif // _WX_PRIVATE_UIACTION_H_