compat: va_copy on Win32 systems
diff --git a/src/cc-compat.h b/src/cc-compat.h
index 507985d..9f23dca 100644
--- a/src/cc-compat.h
+++ b/src/cc-compat.h
@@ -58,4 +58,12 @@
# include <stdbool.h>
#endif
+#ifndef va_copy
+# ifdef __va_copy
+# define va_copy(dst, src) __va_copy(dst, src)
+# else
+# define va_copy(dst, src) ((dst) = (src))
+# endif
+#endif
+
#endif /* INCLUDE_compat_h__ */