Document that SetStatusText() updates the display immediately

This is done by explicitly calling Update() in the generic version and
seems to also be done by the native MSW one, even if it's not documented
to do it.

interface/wx/frame.h

@@ -427,7 +427,11 @@ public:
     void SetStatusBarPane(int n);
 
     /**
-        Sets the status bar text and redraws the status bar.
+        Sets the status bar text and updates the status bar display.
+
+        This is a simple wrapper for wxStatusBar::SetStatusText() which doesn't
+        do anything if the frame has no status bar, i.e. GetStatusBar() returns
+        @NULL.
 
         @param text
             The text for the status field.

interface/wx/statusbr.h

@@ -279,7 +279,9 @@ public:
     /**
         Sets the status text for the @a i-th field.
 
-        The given text will replace the current text.
+        The given text will replace the current text. The display of the status
+        bar is updated immediately, so there is no need to call
+        wxWindow::Update() after calling this function.
 
         Note that if PushStatusText() had been called before the new text will
         also replace the last saved value to make sure that the next call to