Fix include for C++98
Fixes
#pragma once
-#ifdef __cplusplus
+#include "macros.h"
+
+#ifdef CLAP_HAS_CXX11
# include <cstdint>
+#else
+# include <stdint.h>
+#endif
+
+#ifdef __cplusplus
# include <cstddef>
#else
# include <stddef.h>
# include <stdbool.h>
-# include <stdint.h>
#endif
