docu update

doc/tex/grid.tex

@@ -14,6 +14,6 @@ The following different Grid types are available:
 \item[{\large\tt GRID\_CURVILINEAR }]  Curvilinear grid
 \item[{\large\tt GRID\_UNSTRUCTURED}]  Unstructured grid
 \item[{\large\tt GRID\_LCC         }]  Lambert conformal conic grid
-\item[{\large\tt GRID\_REFERENCE      }]  Number of grid
+\item[{\large\tt GRID\_REFERENCE   }]  Grid reference number
 \end{deflist}
 \end{minipage}

src/cdi.h

@@ -129,7 +129,7 @@ extern "C" {
 #define  GRID_LCC2               12  /* Lambert Conformal Conic (PROJ)          */
 #define  GRID_LAEA               13  /* Lambert Azimuthal Equal Area            */
 #define  GRID_SINUSOIDAL         14  /* Sinusoidal                              */
-#define  GRID_REFERENCE          15  /* Reference to the grid                   */
+#define  GRID_REFERENCE          15  /* Grid reference number                   */
 #define  GRID_PROJECTION         16  /* Projected coordiantes                   */
 
 /* ZAXIS types */