msys2: fixed redefined include warnings

src/osgDB/FileNameUtils.cpp

@@ -19,7 +19,9 @@
 #include <osgDB/FileUtils>
 
 #ifdef WIN32
+#if !defined(__MINGW32__)
     #define _WIN32_WINNT 0x0500
+#endif
     #include <windows.h>
 #endif
 

src/osgDB/FileUtils.cpp

@@ -34,7 +34,10 @@ typedef char TCHAR;
     #include <direct.h> // for _mkdir
 
     #define mkdir(x,y) _mkdir((x))
+
+#if !defined(__MINGW32__)
     #define stat64 _stati64
+#endif
 
     // set up for windows so acts just like unix access().
 #ifndef F_OK