Collection of typo fixes.

Use "a" and "an" correctly, mostly in comments. Two error messages were
also fixed (they were just elogs, so no translation work required). Two
function comments in pg_proc.h were also fixed. Etsuro Fujita reported one
of these, but I found a lot more with grep.

Also fix a few other typos spotted while grepping for the a/an typos.
For example, "consists out of ..." -> "consists of ...". Plus a "though"/
"through" mixup reported by Euler Taveira.

Many of these typos were in old code, which would be nice to backpatch to
make future backpatching easier. But much of the code was new, and I didn't
feel like crafting separate patches for each branch. So no backpatching.

Author: hlinnaka

contrib/isn/isn.c

@@ -511,7 +511,7 @@ str2ean(const char *num)
 }
 
 /*
- * ean2string --- Try to convert an ean13 number to an hyphenated string.
+ * ean2string --- Try to convert an ean13 number to a hyphenated string.
  *				  Assumes there's enough space in result to hold
  *				  the string (maximum MAXEAN13LEN+1 bytes)
  *				  This doesn't verify for a valid check digit.

contrib/pg_buffercache/pg_buffercache_pages.c

@@ -142,7 +142,7 @@ pg_buffercache_pages(PG_FUNCTION_ARGS)
 			LWLockAcquire(BufMappingPartitionLockByIndex(i), LW_SHARED);
 
 		/*
-		 * Scan though all the buffers, saving the relevant fields in the
+		 * Scan through all the buffers, saving the relevant fields in the
 		 * fctx->record structure.
 		 */
 		for (i = 0; i < NBuffers; i++)

contrib/spi/timetravel.c

@@ -51,7 +51,7 @@ static EPlan *find_plan(char *ident, EPlan **eplan, int *nplans);
  *			and all other column values as in new tuple, and insert tuple
  *			with old data and stop_date eq current date
  *			ELSE - skip updation of tuple.
- *		2.  IF an delete affects tuple with stop_date eq INFINITY
+ *		2.  IF a delete affects tuple with stop_date eq INFINITY
  *			then insert the same tuple with stop_date eq current date
  *			[ and delete_user eq current user ]
  *			ELSE - skip deletion of tuple.

contrib/test_decoding/expected/decoding_in_xact.out

@@ -11,7 +11,7 @@ SELECT txid_current() = 0;
 SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
 ERROR:  cannot create logical replication slot in transaction that has performed writes
 ROLLBACK;
--- fail because we're creating a slot while in an subxact whose topxact has a xid
+-- fail because we're creating a slot while in a subxact whose topxact has an xid
 BEGIN;
 SELECT txid_current() = 0;
  ?column? 

contrib/test_decoding/specs/ondisk_startup.spec

@@ -36,7 +36,7 @@ step "s3txid" { BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT txid_current() IS
 step "s3c" { COMMIT; }
 
 # Force usage of ondisk snapshot by starting and not finishing a
-# transaction with a assigned xid after consistency has been
+# transaction with an assigned xid after consistency has been
 # reached. In combination with a checkpoint forcing a snapshot to be
 # written and a new restart point computed that'll lead to the usage
 # of the snapshot.

contrib/test_decoding/sql/decoding_in_xact.sql

@@ -7,7 +7,7 @@ SELECT txid_current() = 0;
 SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
 ROLLBACK;
 
--- fail because we're creating a slot while in an subxact whose topxact has a xid
+-- fail because we're creating a slot while in a subxact whose topxact has an xid
 BEGIN;
 SELECT txid_current() = 0;
 SAVEPOINT barf;

doc/src/sgml/ref/insert.sgml

@@ -415,7 +415,7 @@ INSERT INTO <replaceable class="PARAMETER">table_name</replaceable> [ AS <replac
    one or more <replaceable
    class="PARAMETER">column_name_index</replaceable> columns and/or
    <replaceable class="PARAMETER">expression_index</replaceable>
-   expressions, and a optional <replaceable class="PARAMETER">
+   expressions, and an optional <replaceable class="PARAMETER">
    index_predicate</replaceable>.
   </para>
 

src/backend/access/brin/brin_pageops.c

@@ -492,7 +492,7 @@ brin_evacuate_page(Relation idxRel, BlockNumber pagesPerRange,
 /*
  * Return a pinned and exclusively locked buffer which can be used to insert an
  * index item of size itemsz.  If oldbuf is a valid buffer, it is also locked
- * (in a order determined to avoid deadlocks.)
+ * (in an order determined to avoid deadlocks.)
  *
  * If there's no existing page with enough free space to accomodate the new
  * item, the relation is extended.  If this happens, *extended is set to true.

src/backend/access/gin/ginbtree.c

@@ -313,7 +313,7 @@ ginFindParents(GinBtree btree, GinBtreeStack *stack)
  * the parent needs to be updated. (a root split returns true as it doesn't
  * need any further action by the caller to complete)
  *
- * When inserting a downlink to a internal page, 'childbuf' contains the
+ * When inserting a downlink to an internal page, 'childbuf' contains the
  * child page that was split. Its GIN_INCOMPLETE_SPLIT flag will be cleared
  * atomically with the insert. Also, the existing item at the given location
  * is updated to point to 'updateblkno'.

src/backend/access/gin/ginxlog.c

@@ -409,7 +409,7 @@ ginRedoSplit(XLogReaderState *record)
 
 /*
  * VACUUM_PAGE record contains simply a full image of the page, similar to
- * a XLOG_FPI record.
+ * an XLOG_FPI record.
  */
 static void
 ginRedoVacuumPage(XLogReaderState *record)