Add brief documentation for wxLog::Flush().

See #16744.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78309 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/log.h

@@ -506,6 +506,8 @@ public:
 
 
     /**
+        Show all pending output and clear the buffer.
+        
         Some of wxLog implementations, most notably the standard wxLogGui class,
         buffer the messages (for example, to avoid showing the user a zillion of modal
         message boxes one after another -- which would be really annoying).