Fix build errors on windows and osx

Author: unknown

Release/include/cpprest/http_client.h

@@ -43,7 +43,14 @@ typedef void* native_handle;}}}
 #include <memory>
 #include <limits>
 #if !defined(_WIN32) && !defined(__cplusplus_winrt)
-#include <boost/asio/ssl.hpp>
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wconversion"
+#endif
+#include "boost/asio/ssl.hpp"
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
 #endif
 
 #include "pplx/pplxtasks.h"

Release/include/cpprest/http_listener.h

@@ -29,7 +29,7 @@
 #include <limits>
 #include <functional>
 
-#if !defined(_WIN32) || (_WIN32_WINNT >= _WIN32_WINNT_VISTA && !defined(__cplusplus_winrt))
+#if !defined(_WIN32) && !defined(__cplusplus_winrt)
 #include <boost/asio/ssl.hpp>
 #endif