MinGW: Fix compiler warning about winsock2.h and windows.h

This commit fixes following compiler warning with mingw compiler:

In file included from common.h:63:0,
                 from util_security.h:42,
                 from util_security.cc:36:
/usr/share/mingw-w64/include/winsock2.h:15:2: warning: #warning
 Please include winsock2.h before windows.h [-Wcpp]
 #warning Please include winsock2.h before windows.h

README.rst

@@ -361,6 +361,8 @@ environment variable which must fulfill the following conditions:
 
       $NDK/build/tools/make-standalone-toolchain.sh --platform=android-18 --toolchain=arm-linux-androideabi-4.8 --install-dir=$ANDROID_HOME/toolchain
 
+      $NDK/build/tools/make-standalone-toolchain.sh --install-dir=$ANDROID_HOME/toolchain --toolchain=arm-linux-androideabi-4.8 --llvm-version=3.4
+
   You may need to add ``--system=linux-x86_64`` to the above
   command-line for x86_64 Linux host.
 

src/util_security.h

@@ -36,10 +36,11 @@
 #ifndef D_UTIL_SECURITY_H
 #define D_UTIL_SECURITY_H
 
+#include "common.h"
+
 #include <string>
 #include <stdexcept>
 
-#include "common.h"
 #include "a2functional.h"
 #include "MessageDigest.h"