Update submodules: plugins (new commits)

plugins:
    7ecd892 Greg Holmes <greg@dmdirc.com>
            Generify MBassador.

            Gerrit: http://gerrit.dmdirc.com/3772

    87c12df Greg Holmes <greg@dmdirc.com>
            MBassador.

            Depends-On: I2baa7e986ded54930093768238ed24cab8cf4bf7
            Gerrit: http://gerrit.dmdirc.com/3770

Change-Id: Ic09da57829a6231ad9da85ab0f86927ada903c1a