Merge pull request #3154 from gavinandresen/mempool_refactor

Mempool refactor
Improve logging of failed connections
Refactor: pull alert string sanitization into util
New reject p2p message
Test alerts high at high PROTOCOL_VERSIONs

I regenerated the alert test data; now alerts are tested
against a protocol version way above the current protocol
version.

So we won't have to regenerate them every time we bump
PROTOCOL_VERSION in the future.
Bump protocol version to 70002