Add LTR inversion code to diagram generator. This code is used in serveral diagrams and as it modifies a whole diagram it should be central. (This should also make maintenance easier). This function can be called by processors to make sure that their data is plotted with an LTR waterflow.

SYMBOLSET
SYMBOL
  NAME 'point'
  TYPE ELLIPSE
  POINTS
    1 1
  END
  FILLED TRUE
END
SYMBOL
  NAME "square"
  TYPE VECTOR
  POINTS
    0 0
    0 1
    1 1
    1 0
    0 0
  END
  FILLED TRUE
END
END