Fix typos in comments

Author: Daniel Gustafsson <daniel@yesql.se>

src/backend/access/transam/xlogfuncs.c

@@ -175,7 +175,7 @@ pg_stop_backup(PG_FUNCTION_ARGS)
  * The first parameter (variable 'exclusive') allows the user to tell us if
  * this is an exclusive or a non-exclusive backup.
  *
- * The second paramter (variable 'waitforarchive'), which is optional,
+ * The second parameter (variable 'waitforarchive'), which is optional,
  * allows the user to choose if they want to wait for the WAL to be archived
  * or if we should just return as soon as the WAL record is written.
  *

src/include/lib/simplehash.h

@@ -902,7 +902,7 @@ SH_STAT(SH_TYPE * tb)
 #endif   /* SH_DEFINE */
 
 
-/* undefine external paramters, so next hash table can be defined */
+/* undefine external parameters, so next hash table can be defined */
 #undef SH_PREFIX
 #undef SH_KEY_TYPE
 #undef SH_KEY

src/include/nodes/execnodes.h

@@ -569,7 +569,7 @@ typedef struct TupleHashEntryData
 	uint32		hash;			/* hash value (cached) */
 } TupleHashEntryData;
 
-/* define paramters necessary to generate the tuple hash table interface */
+/* define parameters necessary to generate the tuple hash table interface */
 #define SH_PREFIX tuplehash
 #define SH_ELEMENT_TYPE TupleHashEntryData
 #define SH_KEY_TYPE MinimalTuple