Merge branch 'updateui-ischeckable'

Add a flag to wxUpdateUIEvent to tell if the item supports the check
action.

See https://github.com/wxWidgets/wxWidgets/pull/2027

interface/wx/aui/auibar.h

@@ -407,6 +407,13 @@ public:
 
     */
     int GetAlignment() const;
+
+    /**
+        Returns whether the toolbar item can be toggled.
+
+        @since 3.1.5
+     */
+    bool CanBeToggled() const;
 };
 
 /**

interface/wx/event.h

@@ -2374,6 +2374,26 @@ public:
     */
     bool GetEnabled() const;
 
+    /**
+        Returns @true if the UI element can be checked.
+
+        For the event handlers that can be used for multiple items, not all of
+        which can be checked, this method can be useful to determine whether
+        to call Check() on the event object or not, i.e. the main use case for
+        this method is:
+        @code
+        void MyWindow::OnUpdateUI(wxUpdateUIEvent& event)
+        {
+            ....
+            if ( event.IsCheckable() )
+                event.Check(...some condition...);
+        }
+        @endcode
+
+        @since 3.1.5
+    */
+    bool IsCheckable() const;
+
     /**
         Static function returning a value specifying how wxWidgets will send update
         events: to all windows, or only to those which specify that they will process