See issue #2819 for details. The gist is that when we want to send INFO
because we are over the time, we used to send only INFO commands, no
longer sending PING commands. However if a master fails exactly when we
are about to send an INFO command, the PING times will result zero
because the PONG reply was already received, and we'll fail to send more
PINGs, since we try only to send INFO commands: the failure detector
will delay until the connection is closed and re-opened for "long
timeout".

This commit changes the logic so that we can send the three kind of
messages regardless of the fact we sent another one already in the same
code path. It could happen that we go over the message limit for the
link by a few messages, but this is not significant. However now we'll
not introduce delays in sending commands just because there was
something else to send at the same time.

AOF & RDB: be compatible with rdbchecksum no

bugfix for ZPOP: fix the wrong keyc, should be 1

Active defrag fixes for 32bit builds

problems fixed:
* failing to read fragmentation information from jemalloc
* overflow in jemalloc fragmentation hint to the defragger
* test suite not triggering eviction after population

By verifying that it was able to find a regression, and fixing it
accordingly.

- Cluster node structure is now updated after ADDSLOTS

Usually blocking operations make a lot of sense with multiple keys so
that we can listen to multiple queues (or whatever the app models) with
a single connection. However in the synchronous case it is more useful
to be able to ask for N elements. This is a change that I also wanted to
perform soon or later in the blocking list variant, but here it is more
natural since there is no reply type difference.

This commit also adds a top comment about a subtle behavior of mixing
blocking operations of different types in the same key.

Some times it was not released on error, sometimes it was released two
times because the error path expected the "di" var to be NULL if the
iterator was already released. Thanks to @oranagra for pinging me about
potential problems of this kind inside rdb.c.

fix int overflow problem in freeMemoryIfNeeded

- Updated README

An implementation of the
[Ze POP Redis Module](https://github.com/itamarhaber/zpop) as core
Redis commands.

Fixes #1861.

Cluster Manager: fixed argument parsing after --cluster-weight

- Cluster Manager: fixed bug in clusterManagerNodeWithLeastReplicas