Define LUASOCKET_API macro in header file instead of build time argument

--HG--
branch : minor

src/libraries/luasocket/libluasocket/luasocket.h

@@ -18,7 +18,11 @@
 * This macro prefixes all exported API functions
 \*-------------------------------------------------------------------------*/
 #ifndef LUASOCKET_API
-#define LUASOCKET_API extern
+#if defined(WIN32) || defined(_WIN32)
+#       define LUASOCKET_API __declspec(dllexport)
+#else
+#       define LUASOCKET_API __attribute__((visibility("default")))
+#endif
 #endif
 
 /*-------------------------------------------------------------------------*\

src/libraries/luasocket/libluasocket/serial.c

@@ -6,6 +6,7 @@
 
 #include "lua.h"
 #include "lauxlib.h"
+#include "luasocket.h"
 
 #include "auxiliar.h"
 #include "socket.h"