It's not POSIX (BSD systems have -E instead) and we don't actually need it.

Closes #1922

This function failed when an internal-only flag was set as an only flag
in a node: the string was trimmed expecting a final comma before
exiting the function, causing a crash. See issue #4142.
Moreover generation of flags representation only needed at DEBUG log
level was always performed: a waste of CPU time. This is fixed as well
by this commit.

Close #3766.

Issue #4084 shows how for a design error, GEORADIUS is a write command
because of the STORE option. Because of this it does not work
on readonly slaves, gets redirected to masters in Redis Cluster even
when the connection is in READONLY mode and so forth.

To break backward compatibility at this stage, with Redis 4.0 to be in
advanced RC state, is problematic for the user base. The API can be
fixed into the unstable branch soon if we'll decide to do so in order to
be more consistent, and reease Redis 5.0 with this incompatibility in
the future. This is still unclear.

However, the ability to scale GEO queries in slaves easily is too
important so this commit adds two read-only variants to the GEORADIUS
and GEORADIUSBYMEMBER command: GEORADIUS_RO and GEORADIUSBYMEMBER_RO.
The commands are exactly as the original commands, but they do not
accept the STORE and STOREDIST options.

1. brpop last key index, thus checking all keys for slots.
2. Memory leak in clusterRedirectBlockedClientIfNeeded.
3. Remove while loop in clusterRedirectBlockedClientIfNeeded.

Proposed fix to https://github.com/antirez/redis/issues/4027

1. Inline if ... statement if short.
2. No lines over 80 columns.

Fix a few typos/adjust wording in `create-cluster` README

Implement getKeys procedure for georadius and georadiusbymember commands

Close #3993.

Close #3927.

Otherwise, as it was, it will overwrite whatever the user set.

Close #3703.

And many other related Github issues... all reporting the same problem.
There was probably just not enough backlog in certain unlucky runs.
I'll ask people that can reporduce if they see now this as fixed as
well.

commands.

Close #3804.

This reverts commit 153f2f00.

Jemalloc 4.4.0 is apparently causing deadlocks in certain
systems. See for example https://github.com/antirez/redis/issues/3799.
As a cautionary step we are reverting the commit back and
releasing a new stable Redis version.

After investigating issue #3796, it was discovered that MIGRATE
could call migrateCloseSocket() after the original MIGRATE c->argv
was already rewritten as a DEL operation. As a result the host/port
passed to migrateCloseSocket() could be anything, often a NULL pointer
that gets deferenced crashing the server.

Now the socket is closed at an earlier time when there is a socket
error in a later stage where no retry will be performed, before we
rewrite the argument vector. Moreover a check was added so that later,
in the socket_err label, there is no further attempt at closing the
socket if the argument was rewritten.

This fix should resolve the bug reported in #3796.

Ziplists had a bug that was discovered while investigating a different
issue, resulting in a corrupted ziplist representation, and a likely
segmentation foult and/or data corruption of the last element of the
ziplist, once the ziplist is accessed again.

The bug happens when a specific set of insertions / deletions is
performed so that an entry is encoded to have a "prevlen" field (the
length of the previous entry) of 5 bytes but with a count that could be
encoded in a "prevlen" field of a since byte. This could happen when the
"cascading update" process called by ziplistInsert()/ziplistDelete() in
certain contitious forces the prevlen to be bigger than necessary in
order to avoid too much data moving around.

Once such an entry is generated, inserting a very small entry
immediately before it will result in a resizing of the ziplist for a
count smaller than the current ziplist length (which is a violation,
inserting code expects the ziplist to get bigger actually). So an FF
byte is inserted in a misplaced position. Moreover a realloc() is
performed with a count smaller than the ziplist current length so the
final bytes could be trashed as well.

SECURITY IMPLICATIONS:

Currently it looks like an attacker can only crash a Redis server by
providing specifically choosen commands. However a FF byte is written
and there are other memory operations that depend on a wrong count, so
even if it is not immediately apparent how to mount an attack in order
to execute code remotely, it is not impossible at all that this could be
done. Attacks always get better... and we did not spent enough time in
order to think how to exploit this issue, but security researchers
or malicious attackers could.

REPRODUCING:

The bug can be reproduced with the following commands.

    redis-cli del list
    redis-cli rpush list one
    redis-cli rpush list two
    redis-cli rpush list
    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    redis-cli rpush list
    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    redis-cli rpush list three
    redis-cli rpush list a
    redis-cli lrem list 1
    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    redis-cli linsert list after
    AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    10
    redis-cli lrange list 0 -1

Instead of "rpush list a", use "rpush list 10" in order to trigger a
data corruption instead of a crash.

The original jemalloc source tree was modified to:

1. Remove the configure error that prevents nested builds.
2. Insert the Redis private Jemalloc API in order to allow the
Redis fragmentation function to work.