cgribexDefTime: added warning if time axis type changes.

src/stream_cgribex.c

@@ -1571,6 +1571,13 @@ void cgribexDefTime(int *isec1, int vdate, int vtime, int tsteptype, int numavg,
 	  if ( ip2 < 0 || ip2 > 0xFF   ) timetype = TAXIS_ABSOLUTE;
 	}
 
+      static bool lwarn = true;
+      if ( lwarn && timetype == TAXIS_ABSOLUTE )
+        {
+          lwarn = false;
+          Warning("Can't store forecast time %ld %d relative to %ld %d, converted to absolute time!", (long)vdate, vtime, (long)rdate, rtime);
+        }
+
       ISEC1_TimeRange   = timerange;
       ISEC1_TimePeriod1 = ip1;
       ISEC1_TimePeriod2 = ip2;