Fix some typos

Josh Kupershmidt

contrib/unaccent/unaccent.c

@@ -281,7 +281,7 @@ unaccent_lexize(PG_FUNCTION_ARGS)
 		{
 			if (!res)
 			{
-				/* allocate res only it it's needed */
+				/* allocate res only if it's needed */
 				res = palloc0(sizeof(TSLexeme) * 2);
 				res->lexeme = trgchar = palloc(len * pg_database_encoding_max_length() + 1 /* \0 */ );
 				res->flags = TSL_FILTER;

src/backend/access/transam/README

@@ -197,7 +197,7 @@ If a subtransaction requires an XID, we always first assign one to its
 parent.  This maintains the invariant that child transactions have XIDs later
 than their parents, which is assumed in a number of places.
 
-The subsidiary actions of obtaining a lock on the XID and and entering it into
+The subsidiary actions of obtaining a lock on the XID and entering it into
 pg_subtrans and PG_PROC are done at the time it is assigned.
 
 A transaction that has no XID still needs to be identified for various

src/backend/postmaster/postmaster.c

@@ -2506,7 +2506,7 @@ reaper(SIGNAL_ARGS)
 		 * Was it the archiver?  If so, just try to start a new one; no need
 		 * to force reset of the rest of the system.  (If fail, we'll try
 		 * again in future cycles of the main loop.).  Unless we were waiting
-		 * for it to shut down; don't restart it in that case, and and
+		 * for it to shut down; don't restart it in that case, and
 		 * PostmasterStateMachine() will advance to the next shutdown step.
 		 */
 		if (pid == PgArchPID)