Fix volatility marking of pg_size_pretty function

pg_size_pretty function should be marked immutable rather than volatile
because it always returns the same result given the same argument.

Pavel Stehule

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201601221
+#define CATALOG_VERSION_NO	201601271
 
 #endif

src/include/catalog/pg_proc.h

@@ -3583,9 +3583,9 @@ DATA(insert OID = 2332 ( pg_relation_size		PGNSP PGUID 12 1 0 0 0 f f f f t f v
 DESCR("disk space usage for the specified fork of a table or index");
 DATA(insert OID = 2286 ( pg_total_relation_size PGNSP PGUID 12 1 0 0 0 f f f f t f v s 1 0 20 "2205" _null_ _null_ _null_ _null_ _null_ pg_total_relation_size _null_ _null_ _null_ ));
 DESCR("total disk space usage for the specified table and associated indexes");
-DATA(insert OID = 2288 ( pg_size_pretty			PGNSP PGUID 12 1 0 0 0 f f f f t f v s 1 0 25 "20" _null_ _null_ _null_ _null_ _null_ pg_size_pretty _null_ _null_ _null_ ));
+DATA(insert OID = 2288 ( pg_size_pretty			PGNSP PGUID 12 1 0 0 0 f f f f t f i s 1 0 25 "20" _null_ _null_ _null_ _null_ _null_ pg_size_pretty _null_ _null_ _null_ ));
 DESCR("convert a long int to a human readable text using size units");
-DATA(insert OID = 3166 ( pg_size_pretty			PGNSP PGUID 12 1 0 0 0 f f f f t f v s 1 0 25 "1700" _null_ _null_ _null_ _null_ _null_ pg_size_pretty_numeric _null_ _null_ _null_ ));
+DATA(insert OID = 3166 ( pg_size_pretty			PGNSP PGUID 12 1 0 0 0 f f f f t f i s 1 0 25 "1700" _null_ _null_ _null_ _null_ _null_ pg_size_pretty_numeric _null_ _null_ _null_ ));
 DESCR("convert a numeric to a human readable text using size units");
 DATA(insert OID = 2997 ( pg_table_size			PGNSP PGUID 12 1 0 0 0 f f f f t f v s 1 0 20 "2205" _null_ _null_ _null_ _null_ _null_ pg_table_size _null_ _null_ _null_ ));
 DESCR("disk space usage for the specified table, including TOAST, free space and visibility map");