ui.gadgets.tables: implement cell-dim and draw-cell for the f class

basis/ui/gadgets/tables/tables.factor

@@ -67,6 +67,9 @@ rows ;
 GENERIC: cell-dim ( font cell -- width height padding )
 GENERIC: draw-cell ( font cell -- )
 
+M: f cell-dim 2drop 0 0 0 ;
+M: f draw-cell 2drop ;
+
 : single-line ( str -- str' )
     dup [ "\r\n" member? ] any? [ string-lines " " join ] when ;