#290 update to 2.1.5

[Tokio Kikuchi]

Update to 2.1.5 from 2.1.4 earlier checks pending.pck
for duplicate ids and aborts if there is one such
duplication. My mailman installation is fairly old,
have long history and had orphaned pending-ids.
It looked like we can safely ignore such duplication.

[Tokio Kikuchi]

update patch for 2.1.5

[Barry Warsaw]

Logged In: YES
user_id=12800

Thanks! I changed the warning message a bit.