Fix parallel safety markings for pg_start_backup.

Commit 71176854 made pg_start_backup
parallel-restricted rather than parallel-safe, because it now relies
on backend-private state that won't be synchronized with the parallel
worker.  However, it didn't update pg_proc.h.  Separately, Andreas
Karlsson observed that system_views.sql neglected to reiterate the
parallel-safety markings whe redefining various functions, including
this one; so add a PARALLEL RESTRICTED declaration there to match
the new value in pg_proc.h.

src/backend/catalog/system_views.sql

@@ -922,7 +922,8 @@ COMMENT ON FUNCTION ts_debug(text) IS
 
 CREATE OR REPLACE FUNCTION
   pg_start_backup(label text, fast boolean DEFAULT false, exclusive boolean DEFAULT true)
-  RETURNS pg_lsn STRICT VOLATILE LANGUAGE internal AS 'pg_start_backup';
+  RETURNS pg_lsn STRICT VOLATILE LANGUAGE internal AS 'pg_start_backup'
+  PARALLEL RESTRICTED;
 
 -- legacy definition for compatibility with 9.3
 CREATE OR REPLACE FUNCTION

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201604082
+#define CATALOG_VERSION_NO	201605021
 
 #endif

src/include/catalog/pg_proc.h

@@ -3107,7 +3107,7 @@ DATA(insert OID = 2171 ( pg_cancel_backend		PGNSP PGUID 12 1 0 0 0 f f f f t f v
 DESCR("cancel a server process' current query");
 DATA(insert OID = 2096 ( pg_terminate_backend		PGNSP PGUID 12 1 0 0 0 f f f f t f v s 1 0 16 "23" _null_ _null_ _null_ _null_ _null_ pg_terminate_backend _null_ _null_ _null_ ));
 DESCR("terminate a server process");
-DATA(insert OID = 2172 ( pg_start_backup		PGNSP PGUID 12 1 0 0 0 f f f f t f v s 3 0 3220 "25 16 16" _null_ _null_ _null_ _null_ _null_ pg_start_backup _null_ _null_ _null_ ));
+DATA(insert OID = 2172 ( pg_start_backup		PGNSP PGUID 12 1 0 0 0 f f f f t f v r 3 0 3220 "25 16 16" _null_ _null_ _null_ _null_ _null_ pg_start_backup _null_ _null_ _null_ ));
 DESCR("prepare for taking an online backup");
 DATA(insert OID = 2173 ( pg_stop_backup			PGNSP PGUID 12 1 0 0 0 f f f f t f v s 0 0 3220 "" _null_ _null_ _null_ _null_ _null_ pg_stop_backup _null_ _null_ _null_ ));
 DESCR("finish taking an online backup");