test -z "$ac_cv_header_unistd_h" && AC_CHECK_HEADERS(unistd.h)
AC_MSG_CHECKING([whether $1 is declared])
AC_CACHE_VAL(jm_cv_func_decl_$1,
test -z "$ac_cv_header_unistd_h" && AC_CHECK_HEADERS(unistd.h)
AC_MSG_CHECKING([whether $1 is declared])
AC_CACHE_VAL(jm_cv_func_decl_$1,