Update submodules: plugins (new commits)

plugins:
    f21fb8c Greg Holmes <greg@dmdirc.com>
            Use events for statusbar messages.

            Gerrit: http://gerrit.dmdirc.com/3768

    66b5259 Greg Holmes <greg@dmdirc.com>
            Use frame info events in Window menu.

            Gerrit: http://gerrit.dmdirc.com/3765

Change-Id: Id5cba91e81e7686827c7ad73b7ec417b074dbe02