Update RS485 lib include header

Author: sandeepmistry

src/libmodbus/modbus-rtu.cpp

@@ -16,7 +16,7 @@
 #include <assert.h>
 
 #ifdef ARDUINO
-#include <RS485.h>
+#include <ArduinoRS485.h>
 
 #ifndef DEBUG
 #define printf(...) {}