Add static const specification to immutable string table.

src/cdi.h

@@ -578,7 +578,7 @@ int     vlistInqAttTxt(int vlistID, int varID, const char *name, int mlen, char
 /* GRID routines */
 
 void    gridName(int gridtype, char *gridname);
-char   *gridNamePtr(int gridtype);
+const char *gridNamePtr(int gridtype);
 
 void    gridCompress(int gridID);
 

src/cdi_int.h

@@ -279,7 +279,7 @@ void stream_check_ptr(const char *caller, stream_t *streamptr);
 int     streamInqFileID(int streamID);
 
 int     zaxisInqLevelID(int zaxisID, double level);
-char   *gridNamePtr(int gridtype);
+const char *gridNamePtr(int gridtype);
 char   *zaxisNamePtr(int leveltype);
 
 void    streamCheckID(const char *caller, int streamID);

src/grid.c

@@ -26,7 +26,9 @@
 #endif
 
 
-char *Grids[] = {
+/* the value in the second pair of brackets must match the length of
+ * the longest string (including terminating NUL) */
+static const char Grids[][17] = {
   /*  0 */  "undefined",
   /*  1 */  "generic",
   /*  2 */  "gaussian",
@@ -531,9 +533,9 @@ void gridDestroyP ( void * gridptr )
 }
 
 
-char *gridNamePtr(int gridtype)
+const char *gridNamePtr(int gridtype)
 {
-  char *name;
+  const char *name;
   int size = (int) (sizeof(Grids)/sizeof(char *));
 
   if ( gridtype >= 0 && gridtype < size )