Mark pg_start_backup and pg_stop_backup as parallel-restricted.

They depend on backend-private state that will not be synchronized by
the parallel machinery, so they should not be marked parallel-safe.
This issue also exists in 9.6, but we obviously can't do anything
about 9.6 clusters that already exist.  Possibly this could be
back-patched so that future 9.6 clusters would come out OK, or
possibly we should back-patch some other fix, but that would need more
discussion.

David Steele, reviewed by Michael Paquier

Discussion: http://postgr.es/m/CA+TgmoYCWfO2UM-t=HUMFJyxJywLDiLL0nAJpx88LKtvBvNECw@mail.gmail.com

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201703032
+#define CATALOG_VERSION_NO	201703061
 
 #endif

src/include/catalog/pg_proc.h

@@ -3141,9 +3141,9 @@ DATA(insert OID = 2096 ( pg_terminate_backend		PGNSP PGUID 12 1 0 0 0 f f f f t
 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 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_ ));
+DATA(insert OID = 2173 ( pg_stop_backup			PGNSP PGUID 12 1 0 0 0 f f f f t f v r 0 0 3220 "" _null_ _null_ _null_ _null_ _null_ pg_stop_backup _null_ _null_ _null_ ));
 DESCR("finish taking an online backup");
-DATA(insert OID = 2739 ( pg_stop_backup			PGNSP PGUID 12 1 1 0 0 f f f f t t v s 1 0 2249 "16" "{16,3220,25,25}" "{i,o,o,o}" "{exclusive,lsn,labelfile,spcmapfile}" _null_ _null_ pg_stop_backup_v2 _null_ _null_ _null_ ));
+DATA(insert OID = 2739 ( pg_stop_backup			PGNSP PGUID 12 1 1 0 0 f f f f t t v r 1 0 2249 "16" "{16,3220,25,25}" "{i,o,o,o}" "{exclusive,lsn,labelfile,spcmapfile}" _null_ _null_ pg_stop_backup_v2 _null_ _null_ _null_ ));
 DESCR("finish taking an online backup");
 DATA(insert OID = 3813 ( pg_is_in_backup		PGNSP PGUID 12 1 0 0 0 f f f f t f v s 0 0 16 "" _null_ _null_ _null_ _null_ _null_ pg_is_in_backup _null_ _null_ _null_ ));
 DESCR("true if server is in online backup");