Allow using wxWindowUpdateLocker conditionally

This can be useful if the window needs to be frozen only if some
run-time condition holds true.

interface/wx/wupdlock.h

@@ -35,6 +35,17 @@
 class wxWindowUpdateLocker
 {
 public:
+    /**
+        Default constructor doesn't do anything.
+
+        Prefer using the non-default constructor if possible, this constructor
+        is only useful if Lock() must be called conditionally, i.e. if it may
+        or not be called depending on some run-time condition.
+
+        @since 3.1.4
+     */
+    wxWindowUpdateLocker();
+
     /**
         Creates an object preventing the updates of the specified @e win.
         The parameter must be non-@NULL and the window must exist for longer than
@@ -42,6 +53,18 @@ public:
     */
     explicit wxWindowUpdateLocker(wxWindow* win);
 
+    /**
+        Really lock window updates.
+
+        This method can only be called on an object initialized using the
+        default constructor.
+
+        @param win Non-@NULL window which must exist for longer than this object.
+
+        @since 3.1.4
+     */
+    void Lock(wxWindow *win);
+
     /**
         Destructor reenables updates for the window this object is associated with.
     */