Fix incorrect pg_control struct used for PostgreSQL 9.5.

The 9.6 pg_control struct was being used for 9.5. This was not detected by testing because the new field introduced for 9.6 fit into an alignment hole in the 9.5 struct so the size of the struct and offset of all other members did not change. Since the new member was not used there was no impact on functionality.

9.5 is being removed in the next release so the only reason to fix this is to make the diff for that change more sensible, and to document that this happened.

src/postgres/interface/version.vendor.h

@@ -1395,7 +1395,7 @@ typedef struct ControlFileData
 	pg_crc32c	crc;
 } ControlFileData;
 
-#elif PG_VERSION >= PG_VERSION_95
+#elif PG_VERSION >= PG_VERSION_96
 
 /*
  * Contents of pg_control.
@@ -1627,6 +1627,7 @@ typedef struct ControlFileData
 	int			max_worker_processes;
 	int			max_prepared_xacts;
 	int			max_locks_per_xact;
+	bool		track_commit_timestamp;
 
 	/*
 	 * This data is used to check for hardware-architecture compatibility of
@@ -1671,7 +1672,7 @@ typedef struct ControlFileData
 	uint32		data_checksum_version;
 
 	/* CRC of all above ... MUST BE LAST! */
-	pg_crc32	crc;
+	pg_crc32c	crc;
 } ControlFileData;
 
 #endif