Merge pull request #52 from nodemcu/dev094

replace custom stdarg.h header file with the one in gcc toolchain

app/libc/c_stdarg.h

@@ -1,6 +1,12 @@
 #ifndef __c_stdarg_h
 #define __c_stdarg_h
 
+#if defined(__GNUC__)
+
+#include <stdarg.h>
+
+#else
+
 typedef char * va_list;
 
 #define _INTSIZEOF(n)   ((sizeof(n) + sizeof(int) - 1) & ~(sizeof(int) - 1)) 
@@ -11,4 +17,6 @@ typedef char * va_list;
 
 #endif
 
+#endif
+
 /* end of c_stdarg.h */