Silence MSVC C4996 in specific cases

src/desktop/version.cpp

@@ -197,11 +197,21 @@ std::string os_version()
 
 	OSVERSIONINFOEX v { sizeof(OSVERSIONINFOEX) };
 
+#ifdef _MSC_VER
+// GetVersionEx is rather problematic, but it works for our usecase.
+// See https://msdn.microsoft.com/en-us/library/windows/desktop/ms724451(v=vs.85).aspx
+// for more info.
+#pragma warning(push)
+#pragma warning(disable:4996)
+#endif
 	if(!GetVersionEx(reinterpret_cast<OSVERSIONINFO*>(&v))) {
 		ERR_DU << "os_version: GetVersionEx error ("
 			   << GetLastError() << ")\n";
 		return base;
 	}
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
 
 	const DWORD vnum = v.dwMajorVersion * 100 + v.dwMinorVersion;
 	std::string version;

src/network_asio.cpp

@@ -134,7 +134,17 @@ void connection::cancel()
 {
 	if(socket_.is_open()) {
 		boost::system::error_code ec;
+
+#ifdef _MSC_VER
+// Silence warning about boost::asio::basic_socket<Protocol>::cancel always
+// returning an error on XP, which we don't support anymore.
+#pragma warning(push)
+#pragma warning(disable:4996)
+#endif
 		socket_.cancel(ec);
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
 
 		if(ec) {
 			WRN_NW << "Failed to cancel network operations: " << ec.message() << std::endl;

src/wesnothd_connection.cpp

@@ -187,7 +187,17 @@ void wesnothd_connection::cancel()
 	MPTEST_LOG;
 	if(socket_.is_open()) {
 		boost::system::error_code ec;
+
+#ifdef _MSC_VER
+// Silence warning about boost::asio::basic_socket<Protocol>::cancel always
+// returning an error on XP, which we don't support anymore.
+#pragma warning(push)
+#pragma warning(disable:4996)
+#endif
 		socket_.cancel(ec);
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
 
 		if(ec) {
 			WRN_NW << "Failed to cancel network operations: " << ec.message() << std::endl;