Optimize layout of var_t struct.

* xyz can only be one of 123, 132, 213, 231, 312, 321.

src/vlist.h

@@ -46,6 +46,8 @@ typedef struct
 {
   bool isUsed;
   bool flag;
+  short xyz; /* order of spatial dimensions,
+              * a permutation of 123 */
   int mvarID;
   int fvarID;
   int param;
@@ -58,8 +60,7 @@ typedef struct
   int modelID;
   int tableID;
   int timave;
-  int nsb;  // Number of significant bits
-  int xyz;
+  int nsb;           // Number of significant bits
   bool missvalused;  // true if missval is defined
   bool lvalidrange;
   double missval;

src/vlist_var.c

@@ -1327,7 +1327,7 @@ vlistInqVarNSB(int vlistID, int varID)
 static int
 vlistEncodeXyz(const int dimorder[3])
 {
-  return dimorder[0] * 100 + dimorder[1] * 10 + dimorder[2];
+  return (short) (dimorder[0] * 100 + dimorder[1] * 10 + dimorder[2]);
 }
 
 static void
@@ -1376,7 +1376,7 @@ vlistDefVarXYZ(int vlistID, int varID, int xyz)
 
   assert(xyz == 123 || xyz == 312 || xyz == 231 || xyz == 321 || xyz == 132 || xyz == 213);
 
-  vlistptr->vars[varID].xyz = xyz;
+  vlistptr->vars[varID].xyz = (short) xyz;
   reshSetStatus(vlistID, &vlistOps, RESH_DESYNC_IN_USE);
 }