core: fire tx event on replace, expand tests

build: start shipping Ubuntu Artful Aardvark binaries

cmd/faucet: support twitter, google+ and facebook auth too

core/vm: check opcode stack before readonly enforcement

trie: make hasher benchmark meaningful post-caches

core/types: fix test for TransactionsByPriceAndNonce

ethash: fix typo

cmd/puppeth: use dumb textual IP filtering

miner: fix typo

cmd: Added support for downloading to another DB instance

* eth/fetcher: check the origin of filter task

* eth/fetcher: add some details to fetcher logs

If the file already existed, the WriteResponse.Size was being set
as the length of the entire file, not just the amount that was
written to the existing file.

Fixes #15216

The accountCache contains a file cache, and remembers from
scan to scan what files were present earlier. Thus, whenever
there's a change, the scan phase only bothers processing new
and removed files.