Fix an assortment of typos

Author: Alexander Lakhin
Discussion: https://postgr.es/m/ae9f2fcb-4b24-5bb0-4240-efbbbd944ca1@gmail.com

src/backend/access/brin/brin.c

@@ -2598,7 +2598,7 @@ _brin_parallel_heapscan(BrinBuildState *state)
  *
  * After waiting for all workers to finish, merge the per-worker results into
  * the complete index. The results from each worker are sorted by block number
- * (start of the page range). While combinig the per-worker results we merge
+ * (start of the page range). While combining the per-worker results we merge
  * summaries for the same page range, and also fill-in empty summaries for
  * ranges without any tuples.
  *

src/backend/access/transam/slru.c

@@ -228,7 +228,6 @@ SimpleLruAutotuneBuffers(int divisor, int max)
  * name: name of SLRU.  (This is user-visible, pick with care!)
  * nslots: number of page slots to use.
  * nlsns: number of LSN groups per page (set to zero if not relevant).
- * ctllock: LWLock to use to control access to the shared control structure.
  * subdir: PGDATA-relative subdirectory that will contain the files.
  * buffer_tranche_id: tranche ID to use for the SLRU's per-buffer LWLocks.
  * bank_tranche_id: tranche ID to use for the bank LWLocks.

src/backend/access/transam/xlog.c

@@ -8507,7 +8507,7 @@ xlog_redo(XLogReaderState *record)
 
 /*
  * Return the extra open flags used for opening a file, depending on the
- * value of the GUCs wal_sync_method, fsync and io_direct.
+ * value of the GUCs wal_sync_method, fsync and debug_io_direct.
  */
 static int
 get_sync_bit(int method)