add sanity check to zunionInterBlockClientOnSwappedKeys, as the number of keys used is provided as argument to the function

make prototype of custom function to preload keys from the vm match the prototype of waitForMultipleSwappedKeys

AOF writes are now accumulated into a buffer and flushed into disk just before re-entering the event loop. A lot less writes but still this guarantees that AOF is written before the client gets a positive reply about a write operation, as no reply is trasnmitted before re-entering into the event loop.

AOF is now rewritten on slave after SYNC with master. Thanks to @_km for finding this bug and any others'

redis-cli now is able to also output the string representation instead of the raw string. Much better for debugging

Pub/Sub API change: now messages received via pattern matching have a different message type and an additional field representing the original pattern the message matched