twActivate( wHndl )
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     Activate a previously created window. Redraws the frame and places
     titles, in case you are using the two colour definition for
     wFColor which allows one colour for the active window and another
     for inactive ones.

       Arguments:

     wHndl - 'N' Handle of the window to activate. Defaults to the
                 current handle.

       Return:

     Current window handle

       Example:

     twActivate( wHndl )