expr: docu update

doc/tex/mod/Exprf

@@ -89,11 +89,13 @@ Convert x from radians to degrees
 
 Coordinates:
 
-@BeginList clon(x)
+@BeginList gridarea(x)
 @Item = clon(x)
 Longitude coordinate of x (available only if x has geographical coordinates) 
 @Item = clat(x)
 Latitude coordinate of x (available only if x has geographical coordinates) 
+@Item = gridarea(x)
+Grid cell area of x (available only if x has geographical coordinates) 
 @Item = clev(x)
 Level coordinate of x (0, if x is a 2D surface variable)
 @EndList

src/operator_help.h

@@ -1354,9 +1354,10 @@ static const char *ExprHelp[] = {
     "    ",
     "    Coordinates:",
     "    ",
-    "    clon(x)"    "    Longitude coordinate of x (available only if x has geographical coordinates) ",
-    "    clat(x)"    "    Latitude coordinate of x (available only if x has geographical coordinates) ",
-    "    clev(x)"    "    Level coordinate of x (0, if x is a 2D surface variable)",
+    "    clon(x)    "    "    Longitude coordinate of x (available only if x has geographical coordinates) ",
+    "    clat(x)    "    "    Latitude coordinate of x (available only if x has geographical coordinates) ",
+    "    gridarea(x)"    "    Grid cell area of x (available only if x has geographical coordinates) ",
+    "    clev(x)    "    "    Level coordinate of x (0, if x is a 2D surface variable)",
     "    ",
     "    Constants:",
     "    ",