core: fix warning

src/core/error/callstack_windows.cpp

@@ -9,7 +9,10 @@
 
 #include "core/strings/string_stream.h"
 #include <windows.h>
+#pragma warning(push)
+#pragma warning(disable:4091) // 'keyword' : ignored on left of 'type' when no variable is declared
 #include <dbghelp.h>
+#pragma warning(pop)
 
 namespace crown
 {