CLEANUP: assorted typo fixes in the code and comments

This is 13n iteration of typo fixes
diff --git a/src/mqtt.c b/src/mqtt.c
index c906fd4..7679cba 100644
--- a/src/mqtt.c
+++ b/src/mqtt.c
@@ -326,7 +326,7 @@
 }
 
 /* Extracts the value of a <fieldname_id> of type <type> from a given MQTT
- * message <msg>.  IST_NULL is returned if an error occured while parsing or if
+ * message <msg>.  IST_NULL is returned if an error occurred while parsing or if
  * the field could not be found. If more data are required, the message with a
  * length set to 0 is returned. If the field is found, the response is returned
  * as a struct ist.
@@ -858,7 +858,7 @@
 
 	/* parsing payload
 	 *
-	 * Content of payload is realted to flags parsed above and the field order is pre-defined:
+	 * Content of payload is related to flags parsed above and the field order is pre-defined:
 	 *   Client Identifier, Will Topic, Will Message, User Name, Password
 	 */
 	/* read client identifier */