make the configure script die if select() or socket() is missing

configure.in

@@ -628,6 +628,9 @@ AC_CHECK_FUNCS( socket \
 dnl removed 'getpass' check on October 26, 2000
 
 if test "$ac_cv_func_select" != "yes"; then
+  AC_MSG_ERROR(Can't work without an existing select() function)
+fi
+if test "$ac_cv_func_socket" != "yes"; then
   AC_MSG_ERROR(Can't work without an existing socket() function)
 fi