Adding back necessary concrt.h include to ws_winrt.cpp.

Author: stgates

Release/src/websockets/client/ws_winrt.cpp

@@ -25,6 +25,7 @@
 * =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 ****/
 #include "stdafx.h"
+#include <concrt.h>
 
 // ws_winrt only available for Windows Store apps and Windows Phone 8.1
 #if (WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_PC_APP) || (WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_PHONE_APP) && _WIN32_WINNT == _WIN32_WINNT_WINBLUE)) && !defined(CPPREST_EXCLUDE_WEBSOCKETS)