Add version int to HDSLoc

This allows a future HDS wrapper library to be able to quickly
work out which version to use for a given locator.

Author: timj

dat1.h

@@ -123,6 +123,7 @@ typedef enum {
 
 /* Private definition of the HDS locator struct */
 typedef struct LOC {
+  int hds_version;  /* Implementation version number. Always 5 at the moment. */
   void *pntr;       /* Pointer to memory mapped data array [datMap only] */
   size_t bytesmapped; /* Number of bytes mapped into memory [datMap only] */
   size_t vectorized;  /* if 0 not vectorized, else number of vectorized elements */

dat1AllocLoc.c

@@ -101,5 +101,7 @@ dat1AllocLoc( int * status ) {
     emsRep("dat1AllocLoc", "Could not allocate memory for HDS locator",
            status );
   }
+  /* Force the implementation version into the struct */
+  newloc->hds_version = 5;
   return newloc;
 }