Update submodules: plugins (new commits)

plugins:
    67e737c Chris Smith <chris@dmdirc.com>
            Add findbugs.

            Gerrit: http://gerrit.dmdirc.com/3947

Change-Id: I788ce72a91e8aab302c03dfcd50b72e3e3e5c780

modules/plugins

@@ -1 +1 @@
-Subproject commit a519bf92a323959ca9616880228795bb82c099ea
+Subproject commit 67e737c9b45e0c93783cc877cbc5480bcdbcb973