Fixed common misspellings.

Mostly found by 'codespell'.

src/libcharon/bus/bus.h

@@ -177,7 +177,7 @@ struct bus_t {
 	/**
 	 * Send a log message to the bus.
 	 *
-	 * The signal specifies the type of the event occured. The format string
+	 * The signal specifies the type of the event occurred. The format string
 	 * specifies an additional informational or error message with a
 	 * printf() like variable argument list.
 	 * Use the DBG() macros.

src/libcharon/bus/listeners/listener.h

@@ -84,7 +84,7 @@ struct listener_t {
 	/**
 	 * Hook called for received/sent messages of an IKE_SA.
 	 *
-	 * @param ike_sa	IKE_SA sending/receving a message
+	 * @param ike_sa	IKE_SA sending/receiving a message
 	 * @param message	message object
 	 * @param incoming	TRUE for incoming messages, FALSE for outgoing
 	 * @return			TRUE to stay registered, FALSE to unregister