Backwards compatibility: time_t test

[Lars Hecking]

 With the impending release of autoconf 2.54, I am now very close to
 a configure.in that works with both 2.13 and 2.5x.  However, one problem
 remains, and it is quite similar to the one reported by Andreas Bauer a
 few days ago (Subject: Different versions of autoconf cause problems here...)

 The problem is that acconfig.h is now deprecated. I would like to
 remove it completely in one of my projects because it supplies only
 one symbol, but then it won't work with autoconf 2.13.

AC_MSG_CHECKING(for time_t in time.h)
AC_EGREP_HEADER(time_t,time.h,
  [ac_cv_type_time_t=yes
   AC_MSG_RESULT(yes)],
  [AC_MSG_RESULT(no)
   AC_CHECK_TYPE(time_t, long)])

 and acconfig.h contains the definition for time_t.

 Can anyone suggest a test for time_t that works with both 2.13 and 2.5x
 and doesn't require acconfig.h?