Workaround struct redefinition on some newer MinGW header files.

Fix #1899.

Source/ThirdParty/SDL/CMakeLists.txt

@@ -1111,6 +1111,14 @@ elseif(WINDOWS)
   if(DIRECTX)
     # Urho3D - bug fix - use our own FindDirectX.cmake module which does not rely on DXSDK_DIR environment variable directly when DirectX SDK is being used
     # Urho3D - TODO - move the find_package(DirectX) call from Urho3D common module to here later after we have refactored the library dependency handling
+
+    check_struct_has_member (XINPUT_GAMEPAD_EX wButtons xinput.h HAVE_XINPUT_GAMEPAD_EX)
+    check_struct_has_member (XINPUT_STATE_EX dwPacketNumber xinput.h HAVE_XINPUT_STATE_EX)
+    foreach (VAR HAVE_XINPUT_GAMEPAD_EX HAVE_XINPUT_STATE_EX)
+      if (${VAR})
+        add_definitions (-D${VAR})
+      endif ()
+    endforeach ()
   endif()
 
   if(SDL_AUDIO)

Source/ThirdParty/SDL/src/core/windows/SDL_xinput.h

@@ -18,6 +18,9 @@
      misrepresented as being the original software.
   3. This notice may not be removed or altered from any source distribution.
 */
+
+// Modified by Yao Wei Tjong for Urho3D
+
 #include "../../SDL_internal.h"
 
 #ifndef _SDL_xinput_h
@@ -100,6 +103,8 @@
 #endif
 
 /* typedef's for XInput structs we use */
+// Urho3D - declara only when built-in xinput.h hasn't declared it
+#ifndef HAVE_XINPUT_GAMEPAD_EX
 typedef struct
 {
     WORD wButtons;
@@ -111,12 +116,14 @@ typedef struct
     SHORT sThumbRY;
     DWORD dwPaddingReserved;
 } XINPUT_GAMEPAD_EX;
-
+#endif
+#ifndef HAVE_XINPUT_STATE_EX
 typedef struct
 {
     DWORD dwPacketNumber;
     XINPUT_GAMEPAD_EX Gamepad;
 } XINPUT_STATE_EX;
+#endif
 
 typedef struct
 {