Added workaround in DNSCache for assertion in twisted's reactor.callLater

Ignore-this: a89e8e5d31d6309b9486c3c6f2e8de94

darcs-hash:20100121144031-1e3d8-5e03d5bf9091162bbb8daa1a7c7108e6eb6776d6
Updated copyright years

Ignore-this: 9c9643cbb207efa3fac9e0db390d8d74

darcs-hash:20100122123847-1e3d8-682583b2e78d9020b94664fd76697c6cb532e083