Also call wxAuiManager::UnInit() when manager itself is destroyed

This completes the changes of the previous commit and should ensure that
UnInit() is always called, whoever is destroyed first -- the managed
window or the manager itself.

Also update the documentation to mention that calling UnInit()
explicitly is not necessary any longer.

interface/wx/aui/framemanager.h

@@ -484,11 +484,12 @@ public:
     void StartPaneDrag(wxWindow* paneWindow, const wxPoint& offset);
 
     /**
-        Uninitializes the framework and should be called before a managed frame or
-        window is destroyed. UnInit() is usually called in the managed wxFrame's
-        destructor.  It is necessary to call this function before the managed frame
-        or window is destroyed, otherwise the manager cannot remove its custom event
-        handlers from a window.
+        Dissociate the managed window from the manager.
+
+        This function may be called before the managed frame or window is
+        destroyed, but, since wxWidgets 3.1.4, it's unnecessary to call it
+        explicitly, as it will be called automatically when this window is
+        destroyed, as well as when the manager itself is.
     */
     void UnInit();
 

samples/aui/auidemo.cpp

@@ -116,8 +116,6 @@ public:
             const wxSize& size = wxDefaultSize,
             long style = wxDEFAULT_FRAME_STYLE | wxSUNKEN_BORDER);
 
-    ~MyFrame();
-
     wxAuiDockArt* GetDockArt();
     void DoUpdate();
 
@@ -1016,11 +1014,6 @@ MyFrame::MyFrame(wxWindow* parent,
     m_mgr.Update();
 }
 
-MyFrame::~MyFrame()
-{
-    m_mgr.UnInit();
-}
-
 wxAuiDockArt* MyFrame::GetDockArt()
 {
     return m_mgr.GetArtProvider();

src/aui/framemanager.cpp

@@ -633,6 +633,8 @@ wxAuiManager::wxAuiManager(wxWindow* managed_wnd, unsigned int flags)
 
 wxAuiManager::~wxAuiManager()
 {
+    UnInit();
+
     // NOTE: It's possible that the windows have already been destroyed by the
     // time this dtor is called, so this loop can result in memory access via
     // invalid pointers, resulting in a crash.  So it will be disabled while
@@ -953,9 +955,10 @@ void wxAuiManager::SetManagedWindow(wxWindow* wnd)
 }
 
 
-// UnInit() must be called, usually in the destructor
-// of the frame class.   If it is not called, usually this
-// will result in a crash upon program exit
+// UnInit() is called automatically by wxAuiManager itself when either the
+// manager itself or its associated frame is destroyed, but can also be called
+// explicitly, so make it safe to call it multiple times and just do nothing
+// during any calls but the first one.
 void wxAuiManager::UnInit()
 {
     if (m_frame)