Fix compiler warnings.

Change-Id: I56e2062a3074d39153c30aa0eaecce94408295e2
Reviewed-on: http://gerrit.dmdirc.com/3574
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>
Update submodules: plugins (new commits)

plugins:
    3feb3bb Greg Holmes <greg@dmdirc.com>
            Fix compiler warnings.

            Gerrit: http://gerrit.dmdirc.com/3573

Change-Id: Id76633ee2efed8358b132db9973d87644910fa82