[PATCH] configure: remove unused vars

[Joe Orton]

Second configure patch: these three variables are set but never used:

(these patches may not apply out-of-order, I'll resend if necessary)

--- configure.in.first  Fri Sep 13 09:40:40 2002
+++ configure.in        Fri Sep 13 09:43:59 2002
@@ -562,9 +562,6 @@
     fi
 fi
 
-ac_cv_define_READDIR_IS_THREAD_SAFE=no
-ac_cv_define_GETHOSTBYNAME_IS_THREAD_SAFE=no
-ac_cv_define_GETHOSTBYADDR_IS_THREAD_SAFE=no
 if test "$threads" = "1"; then
     echo "APR will use threads"
     AC_CHECK_LIB(c_r, readdir,