Rework every uint8 to byte and rework every []byte to bytes.Buffer

I just learnt that uint8 and byte are the fucking same
And that bytes.Buffer is the thing to use
Idiot idiot idiot...
Live and learn

pdu/cancel.go

@@ -5,11 +5,11 @@ type (
 		header           PDU_HEADER
 		service_type     string
 		message_id       string
-		source_addr_ton  uint8
-		source_addr_npi  uint8
+		source_addr_ton  byte
+		source_addr_npi  byte
 		source_addr      string
-		dest_addr_ton    uint8
-		dest_addr_npi    uint8
+		dest_addr_ton    byte
+		dest_addr_npi    byte
 		destination_addr string
 	}
 	CANCEL_SM_RESP struct {