Adds AU tail number decoding from ICAO addr.

Contribution by @armeniki. #736.

main/traffic.go

@@ -1164,11 +1164,13 @@ func updateDemoTraffic(icao uint32, tail string, relAlt float32, gs float64, off
 				but are not used for aicraft on the civil registry. These could be
 				military, other public aircraft, or future use.
 
-
 				Values between C0CDF9 - C3FFFF are allocated to Canada,
 				but are not used for aicraft on the civil registry. These could be
 				military, other public aircraft, or future use.
 
+				Values between 7C0000 - 7FFFFF are allocated to Australia.
+
+
 			Output:
 				string: String containing the decoded tail number (if decoding succeeded),
 					"NON-NA" (for non-US / non Canada allocation), and "US-MIL" or "CA-MIL" for non-civil US / Canada allocation.
@@ -1189,9 +1191,11 @@ func icao2reg(icao_addr uint32) (string, bool) {
 		nation = "US"
 	} else if (icao_addr >= 0xC00001) && (icao_addr <= 0xC3FFFF) {
 		nation = "CA"
+	} else if (icao_addr >= 0x7C0000) && (icao_addr <= 0x7FFFFF) {
+		nation = "AU"
 	} else {
 		//TODO: future national decoding.
-		return "NON-NA", false
+		return "OTHER", false
 	}
 
 	if nation == "CA" { // Canada decoding
@@ -1222,6 +1226,29 @@ func icao2reg(icao_addr uint32) (string, bool) {
 		tail = fmt.Sprintf("C-%c%c%c%c", b_str[b], c+65, d+65, e+65)
 	}
 
+	if nation == "AU" { // Australia decoding
+
+		nationalOffset := uint32(0x7C0000)
+		offset := (icao_addr - nationalOffset)
+		i1 := offset / 1296
+		offset2 := offset % 1296
+		i2 := offset2 / 36
+		offset3 := offset2 % 36
+		i3 := offset3
+
+		var a_char, b_char, c_char string
+
+		a_char = fmt.Sprintf("%c", i1+65)
+		b_char = fmt.Sprintf("%c", i2+65)
+		c_char = fmt.Sprintf("%c", i3+65)
+
+		if i1 < 0 || i1 > 25 || i2 < 0 || i2 > 25 || i3 < 0 || i3 > 25 {
+			return "OTHER", false
+		}
+
+		tail = "VH-" + a_char + b_char + c_char
+	}
+
 	if nation == "US" { // FAA decoding
 		// First, discard addresses that are not assigned to aircraft on the civil registry
 		if icao_addr > 0xADF7C7 {