Add wxMenuItem::GetBitmapBundle()

This is needed to e.g. allow cloning a wxMenuItem fully without losing
any of its data.

include/wx/menuitem.h

@@ -118,6 +118,10 @@ public:
     // bitmap-related functions
 
     virtual void SetBitmap(const wxBitmapBundle& bmp);
+    wxBitmapBundle GetBitmapBundle() const { return m_bitmap; }
+
+    // This method only exists for compatibility, prefer using
+    // GetBitmapBundle() in the new code.
     virtual wxBitmap GetBitmap() const;
 
 #if wxUSE_ACCEL

interface/wx/menuitem.h

@@ -162,6 +162,9 @@ public:
 
     /**
         Returns the item bitmap.
+
+        This method exists only for compatibility, please use GetBitmapBundle()
+        in the new code.
     */
     wxBitmap GetBitmap() const;
 
@@ -172,6 +175,18 @@ public:
     */
     wxBitmap GetBitmap(bool checked) const;
 
+    /**
+        Returns the bitmap bundle containing the bitmap used for this item.
+
+        The returned bundle is invalid, i.e. empty, if no bitmap is associated
+        with the item.
+
+        @see SetBitmap()
+
+        @since 3.2.0
+    */
+    wxBitmapBundle GetBitmapBundle() const;
+
     /**
         Returns the bitmap used for disabled items.