Fixed SystemClock_Config declaration

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/stm32_def.h

@@ -78,7 +78,13 @@
 #define CAN1 CAN
 #endif
 
+#ifdef __cplusplus
+extern "C"{
+#endif // __cplusplus
 // weaked functions declaration
 void SystemClock_Config(void);
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus
 
 #endif //_STM32_DEF_

cores/arduino/wiring.h

@@ -29,14 +29,6 @@
 #include "binary.h"
 #include "itoa.h"
 
-#ifdef __cplusplus
-extern "C"{
-#endif // __cplusplus
-#include <board.h>
-#ifdef __cplusplus
-}
-#endif
-
 #include "wiring_analog.h"
 #include "wiring_constants.h"
 #include "wiring_digital.h"
@@ -45,6 +37,14 @@ extern "C"{
 #include "wiring_time.h"
 #include "WInterrupts.h"
 
+#ifdef __cplusplus
+extern "C"{
+#endif // __cplusplus
+#include <board.h>
+#ifdef __cplusplus
+}
+#endif
+
 #ifdef __cplusplus
 #include "HardwareSerial.h"
 #include "Tone.h"