Improve PostgreSQL version check

Author: mperice

imgsmlr.c

@@ -13,9 +13,11 @@
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
-#ifndef VARDATA_ANY
+#ifdef PG_VERSION_NUM
+#if PG_VERSION_NUM >= 160000
 #include "varatt.h"
 #endif
+#endif
 
 #include "c.h"
 #include "fmgr.h"

imgsmlr_idx.c

@@ -13,9 +13,12 @@
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
-#ifndef VARDATA_ANY
+
+#ifdef PG_VERSION_NUM
+#if PG_VERSION_NUM >= 160000
 #include "varatt.h"
 #endif
+#endif
 
 #include "fmgr.h"
 #include "imgsmlr.h"