Move EXTERN_C to util.h

src/util.h

@@ -27,6 +27,14 @@ void mg_usleep(unsigned long usecs);
 #define mg_htons(x) mg_ntohs(x)
 #define mg_htonl(x) mg_ntohl(x)
 
+#ifndef EXTERN_C
+#ifdef __cplusplus
+#define EXTERN_C extern "C"
+#else
+#define EXTERN_C
+#endif
+#endif
+
 // Expands to a string representation of its argument: e.g.
 // MG_STRINGIFY_LITERAL(5) expands to "5"
 #if !defined(_MSC_VER) || _MSC_VER >= 1900