AC_CHECK_HEADERS([sys/param.h])
AC_CHECK_HEADERS([sys/select.h])
AC_CHECK_HEADERS([sys/stat.h])
+AC_CHECK_HEADERS([sys/sysctl.h])
AC_CHECK_HEADERS([sys/time.h])
AC_CHECK_HEADERS([sys/types.h])
AC_CHECK_HEADERS([unistd.h])
AC_CHECK_FUNCS([gettimeofday])
AC_CHECK_FUNCS([usleep])
AC_CHECK_FUNCS([vasprintf])
+AC_CHECK_FUNCS([realpath])
# guess-rev.sh only exists in the repository, not in the released archives
AC_MSG_CHECKING([whether to build a release])