added regression test for clean compilation when including windows.h

Thanks to Mark Rivers who suggested this test.

test/compiler/include_windows_h.st

+program include_windows_h
+
+#ifdef _WIN32
+%%#include <windows.h>
+#endif
+
+#include "simple.st"

test/compiler/snc_test.plt

@@ -8,6 +8,7 @@ my $success = {
   sncExOpt_DuplOpt => 0,
   sync_not_monitored => 0,
   syncq_not_monitored => 0,
+  include_windows_h => 0,
 };
 
 my $warning = {