port upgrade does nothing with a downgraded package

[yaseppochi (Stephen J. Turnbull)]

Specifically, in the following sequence

# port outdated
The following installed ports are outdated:
autoconf                       2.63_0 < 2.64_0           
# port deactivate autoconf @2.64_0
# port deactivate autoconf @2.63_0
# port upgrade autoconf
# port outdated
The following installed ports are outdated:
autoconf                       2.63_0 < 2.64_0           
}}
'port upgrade' does nothing and says nothing about the situation.  It seems to me that port *should* do the upgrade.  However, if there's a reason not to do that, it should report that it isn't doing it and suggest a deactivate ... activate cycle instead.