Update submodules: plugins (new commits)

plugins:
    c20831a Greg Holmes <greg@dmdirc.com>
            Use frame info events in Button bar.

            Gerrit: http://gerrit.dmdirc.com/3763

    7df5ab2 Greg Holmes <greg@dmdirc.com>
            Convert treeview to event frame info.

            Gerrit: http://gerrit.dmdirc.com/3764

Change-Id: Ie96e870d4a771169ec2a93174cdd52a0eea8f247