Fix typos in comments

The changes done in this commit impact comments with no direct
user-visible changes, with fixes for incorrect function, variable or
structure names.

Author: Alexander Lakhin
Discussion: https://postgr.es/m/e8c38840-596a-83d6-bd8d-cebc51111572@gmail.com

src/backend/utils/activity/backend_status.c

@@ -283,7 +283,7 @@ pgstat_beinit(void)
  *
  *	Apart from auxiliary processes, MyBackendId, MyDatabaseId,
  *	session userid, and application_name must be set for a
- *	backend (hence, this cannot be combined with pgbestat_beinit).
+ *	backend (hence, this cannot be combined with pgstat_beinit).
  *	Note also that we must be inside a transaction if this isn't an aux
  *	process, as we may need to do encoding conversion on some strings.
  * ----------

src/backend/utils/activity/pgstat_wal.c

@@ -24,7 +24,7 @@
 PgStat_PendingWalStats PendingWalStats = {0};
 
 /*
- * WAL usage counters saved from pgWALUsage at the previous call to
+ * WAL usage counters saved from pgWalUsage at the previous call to
  * pgstat_report_wal(). This is used to calculate how much WAL usage
  * happens between pgstat_report_wal() calls, by subtracting
  * the previous counters from the current ones.

src/backend/utils/adt/acl.c

@@ -4717,8 +4717,8 @@ pg_has_role_id_id(PG_FUNCTION_ARGS)
  *		Convert text string to AclMode value.
  *
  * We use USAGE to denote whether the privileges of the role are accessible
- * (has_privs), MEMBER to denote is_member, and MEMBER WITH GRANT OPTION
- * (or ADMIN OPTION) to denote is_admin.  There is no ACL bit corresponding
+ * (has_privs_of_role), MEMBER to denote is_member, and MEMBER WITH GRANT
+ * (or ADMIN) OPTION to denote is_admin.  There is no ACL bit corresponding
  * to MEMBER so we cheat and use ACL_CREATE for that.  This convention
  * is shared only with pg_role_aclcheck, below.
  */

src/backend/utils/adt/pg_locale.c

@@ -1012,7 +1012,7 @@ search_locale_enum(LPWSTR pStr, DWORD dwFlags, LPARAM lparam)
 	{
 		/*
 		 * If the enumerated locale does not have a hyphen ("en") OR the
-		 * lc_message input does not have an underscore ("English"), we only
+		 * locale_name input does not have an underscore ("English"), we only
 		 * need to compare the <Language> tags.
 		 */
 		if (wcsrchr(pStr, '-') == NULL || wcsrchr(argv[0], '_') == NULL)

src/backend/utils/adt/selfuncs.c

@@ -4210,7 +4210,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			 * Process complex expressions, not just simple Vars.
 			 *
 			 * First, we search for an exact match of an expression. If we
-			 * find one, we can just discard the whole GroupExprInfo, with all
+			 * find one, we can just discard the whole GroupVarInfo, with all
 			 * the variables we extracted from it.
 			 *
 			 * Otherwise we inspect the individual vars, and try matching it

src/backend/utils/mb/mbutils.c

@@ -453,7 +453,7 @@ pg_do_encoding_conversion(unsigned char *src, int len,
  *
  * The output is null-terminated.
  *
- * If destlen < srclen * MAX_CONVERSION_LENGTH + 1, the converted output
+ * If destlen < srclen * MAX_CONVERSION_INPUT_LENGTH + 1, the converted output
  * wouldn't necessarily fit in the output buffer, and the function will not
  * convert the whole input.
  *