devel/autogen upgrade will fail. UPDATING needs an entry

[Kevin Oberman]

Upgrading devel/autogen will fail as the build procedure will attempt to
run the new version, but will find the old library version and error.

An entry in UPDATING to the effect that "pkg delete autogen" should by run
and then autogen should be reinstalled.

This does not apply up upgrading with pkg or building with poudriere.
--
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman at gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683