Update available.adoc

Fixes the issue with BYTE keyword that is no longer supported, fixing arduino#320

Author: SimonePDA

Language/Functions/Communication/Serial/available.adoc

@@ -82,13 +82,13 @@ void loop() {
   // read from port 0, send to port 1:
   if (Serial.available()) {
     int inByte = Serial.read();
-    Serial1.print(inByte, BYTE);
+    Serial1.print(inByte, DEC);
 
   }
   // read from port 1, send to port 0:
   if (Serial1.available()) {
     int inByte = Serial1.read();
-    Serial.print(inByte, BYTE);
+    Serial.print(inByte, DEC);
   }
 }
 ----