Simplify secure API functions workaround for MinGW

src/platform-win32.cc

Index: src/platform-win32.cc
===================================================================
--- src/platform-win32.cc	(revision 13605)
+++ src/platform-win32.cc	(working copy)
@@ -27,6 +27,17 @@
 
 // Platform specific code for Win32.
 
+// Secure API functions are not available using MinGW with msvcrt.dll
+// on Windows XP. Make sure MINGW_HAS_SECURE_API is not defined to
+// disable definition of secure API functions in standard headers that
+// would conflict with our own implementation.
+#ifdef __MINGW32__
+#include <_mingw.h>
+#ifdef MINGW_HAS_SECURE_API
+#undef MINGW_HAS_SECURE_API
+#endif  // MINGW_HAS_SECURE_API
+#endif  // __MINGW32__
+
 #define V8_WIN32_HEADERS_FULL
 #include "win32-headers.h"
 
@@ -65,14 +76,6 @@
 #endif  // __MINGW64_VERSION_MAJOR
 
 
-#ifdef MINGW_HAS_SECURE_API
-#define localtime_s  v8_localtime_s
-#define fopen_s      v8_fopen_s
-#define _vsnprintf_s v8_vsnprintf_s
-#define strncpy_s    v8_strncpy_s
-#endif  // MINGW_HAS_SECURE_API
-
-
 int localtime_s(tm* out_tm, const time_t* time) {
   tm* posix_local_time_struct = localtime(time);
   if (posix_local_time_struct == NULL) return 1;
@@ -818,10 +821,6 @@
 
 #undef _TRUNCATE
 #undef STRUNCATE
-#undef localtime_s
-#undef fopen_s
-#undef _vsnprintf_s
-#undef strncpy_s
 
 // We keep the lowest and highest addresses mapped as a quick way of
 // determining that pointers are outside the heap (used mostly in assertions