AC_DEFUN([CONFIG_EXTRA],[

         AH_TOP([
#pragma once

/* _SYS_FEATURE_TESTS_H is Solaris, _FEATURES_H is GCC */
#if defined( _SYS_FEATURE_TESTS_H) || defined(_FEATURES_H)
#error "You should include config.h as your first include file"
#endif

                ])
         ])