Thanks to @JohnSully for noticing this problem.

these had severe impact for small zsets, for instance ones with just one
element that is longer than 64 (causing it not to be ziplist encoded)

for instance detached thread safe contexts, or various callbacks that don't
provide a context.

See for reference PR #6337. Thanks to @git-hulk for spotting this.

Related to #6296.

RM_ReplyWithCString was missing registration

backport module rdb aux data into 5.0

(cherry picked from commit 0a97149d)

When implementing the code that saves and loads these aux fields we used rdb
format that was added for that in redis 5.0, but then we added the 'when' field
which meant that the old redis-check-rdb won't be able to skip these.
this fix adds an opcode as if that 'when' is part of the module data.

(cherry picked from commit 3bfcae24)

Other changes:
* fix memory leak in error handling of rdb loading of type OBJ_MODULE

(cherry picked from commit 3b6aeea4)

Before this commit we may have not consumer buffers when a read error is
encountered. Such buffers may contain errors that are important clues
for the user: for instance a protocol error in the payload we send in
pipe mode will cause the server to abort the connection. If the user
does not get the protocol error, debugging what is happening can be a
nightmare.

This commit fixes issue #3756.

Signed-off-by: NItamar Haber <itamar@redislabs.com>

Signed-off-by: NItamar Haber <itamar@redislabs.com>

CLIENT PAUSE may be used, in other contexts, for a long time making all
the slaves time out. Better for now to be more specific about what
should disable senidng PINGs.

An alternative to that would be to virtually refresh the slave
interactions when clients are paused, however for now I went for this
more conservative solution.

In fast systems "SLOWLOG RESET" is fast enough to don't be logged even
when the time limit is "1" sometimes. Leading to false positives such
as:

[err]: SLOWLOG - can be disabled in tests/unit/slowlog.tcl
Expected '1' to be equal to '0'

sdsTest() defined in sds.c dit not match the call in server.c.
remove it from REDIS_TEST, since test-sds defined in Makefile.

solving few replication related tests race conditions which fail on slow machines

bugfix in slave buffers test: since the test is executed twice, each time with
a different commands count, the threshold for the delta can't be a constant.

Add a flag to automatically protect filters from being called
recursively by their own module.

A filter handle is returned and can be used to unregister a filter.  In
the future it can also be used to further configure or manipulate the
filter.

Filters are now automatically unregistered when a module unloads.