Remove some warnings when compiling with mingw (mingw-w64, 32 bits)

Reviewed-by: Ramiro Polla <ramiro.polla@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/network.h

@@ -31,9 +31,21 @@
 #include <winsock2.h>
 #include <ws2tcpip.h>
 
+#ifdef EPROTONOSUPPORT
+# undef EPROTONOSUPPORT
+#endif
 #define EPROTONOSUPPORT WSAEPROTONOSUPPORT
+#ifdef ETIMEDOUT
+# undef ETIMEDOUT
+#endif
 #define ETIMEDOUT       WSAETIMEDOUT
+#ifdef ECONNREFUSED
+# undef ECONNREFUSED
+#endif
 #define ECONNREFUSED    WSAECONNREFUSED
+#ifdef EINPROGRESS
+# undef EINPROGRESS
+#endif
 #define EINPROGRESS     WSAEINPROGRESS
 
 int ff_neterrno(void);

libavformat/os_support.h

@@ -31,6 +31,9 @@
 
 #if defined(__MINGW32__) && !defined(__MINGW32CE__)
 #  include <fcntl.h>
+#  ifdef lseek
+#   undef lseek
+#  endif
 #  define lseek(f,p,w) _lseeki64((f), (p), (w))
 #  define stat _stati64
 #  define fstat(f,s) _fstati64((f), (s))