Cleanup uartout declaration

Firmware/Marlin.h

@@ -65,16 +65,6 @@
 
 #include "lcd.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-extern FILE _uartout;
-#ifdef __cplusplus
-}
-#endif
-
-#define uartout (&_uartout)
-
 #define SERIAL_PROTOCOL(x) (MYSERIAL.print(x))
 #define SERIAL_PROTOCOL_F(x,y) (MYSERIAL.print(x,y))
 #define SERIAL_PROTOCOLPGM(x) (serialprintPGM(PSTR(x)))

Firmware/Marlin_main.cpp

@@ -773,9 +773,8 @@ static void factory_reset(char level)
 	}
 }
 
-extern "C" {
-FILE _uartout; //= {0}; Global variable is always zero initialized. No need to explicitly state this.
-}
+static FILE _uartout;
+#define uartout (&_uartout)
 
 int uart_putchar(char c, FILE *)
 {