Fix misc typos.

Oskari Saarenmaa. Backpatch to stable branches where applicable.

src/backend/access/common/heaptuple.c

@@ -807,7 +807,7 @@ heap_modify_tuple(HeapTuple tuple,
 	 * repl information, as appropriate.
 	 *
 	 * NOTE: it's debatable whether to use heap_deform_tuple() here or just
-	 * heap_getattr() only the non-replaced colums.  The latter could win if
+	 * heap_getattr() only the non-replaced columns.  The latter could win if
 	 * there are many replaced columns and few non-replaced ones. However,
 	 * heap_deform_tuple costs only O(N) while the heap_getattr way would cost
 	 * O(N^2) if there are many non-replaced columns, so it seems better to

src/backend/access/gin/ginfast.c

@@ -886,8 +886,8 @@ ginInsertCleanup(GinState *ginstate,
 												 * locking */
 
 			/*
-			 * remove readed pages from pending list, at this point all
-			 * content of readed pages is in regular structure
+			 * remove read pages from pending list, at this point all
+			 * content of read pages is in regular structure
 			 */
 			if (shiftList(index, metabuffer, blkno, stats))
 			{

src/backend/access/gist/gistproc.c

@@ -578,7 +578,7 @@ gist_box_picksplit(PG_FUNCTION_ARGS)
 		 * We first consider splits where b is the lower bound of an entry.
 		 * We iterate through all entries, and for each b, calculate the
 		 * smallest possible a. Then we consider splits where a is the
-		 * uppper bound of an entry, and for each a, calculate the greatest
+		 * upper bound of an entry, and for each a, calculate the greatest
 		 * possible b.
 		 *
 		 * In the above example, the first loop would consider splits:
@@ -628,7 +628,7 @@ gist_box_picksplit(PG_FUNCTION_ARGS)
 		}
 
 		/*
-		 * Iterate over upper bound of left group finding greates possible
+		 * Iterate over upper bound of left group finding greatest possible
 		 * lower bound of right group.
 		 */
 		i1 = nentries - 1;