The log says:
error: dependent using declaration resolved to type without 'typename'
However the log also says:
:debug:main Skipping completed org.macports.archivefetch (poco)
:debug:main Skipping completed org.macports.fetch (poco)
:debug:main Skipping completed org.macports.checksum (poco)
:debug:main Skipping completed org.macports.extract (poco)
:debug:main Skipping completed org.macports.patch (poco)
:debug:main Skipping completed org.macports.configure (poco)
which means this was not a clean attempt. Please "sudo port clean poco" and try again, and if it fails again, attach the new main.log to this ticket.
There is a new version of poco to which we could try to update the port.