Add format check to debug()

Author: kjbracey

platform/mbed_debug.h

@@ -27,11 +27,14 @@
 #include <stdio.h>
 #include <stdarg.h>
 #endif
+#include "mbed_toolchain.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+static inline void debug(const char *format, ...) MBED_PRINTF(1, 2);
+static inline void debug_if(int condition, const char *format, ...) MBED_PRINTF(2, 3);
 
 /** Output a debug message
  *