Typo fixes in CONTRIBUTING

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.

fix cluster failover time out

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'

Now clients that are ready to be terminated asynchronously are processed
more often in beforeSleep() instead of being processed in serverCron().
This means that the test will not be able to catch the moment the client
was terminated, also note that the 'omem' figure now changes in big
steps, because of the new client output buffers layout.

So we have to change the test range in order to accomodate for that.
Yet the test is useful enough to be worth taking, even if its precision
is reduced by this commit. Probably if we get more problems, a thing
that makes sense is just to check that the limit is < 200k. That's more
than enough actually.

aof: enhance AOF_FSYNC_EVERYSEC, more details in #5985

Do not active expire keys in the background when the switch is off.

Makefile: 1TD -> STD

Preserve client->id for blocked clients.

change the comments there may have a mis type

delete sdsTest() from REDIS_TEST in server.c to fix build failed

fix-inappropriate-add-operation-code

Fix uint64_t hash value in active defrag

[Minor] Fix build warnings on Linux

test cases: skiptill -> skip-till

Enlarge error buffer in redis-check-aof.c to remove compiler warning of output truncation through snprintf format string

Hi, @antirez

In the code, to get the size of ziplist, "unsigned int bytes = ZIPLIST_HEADER_SIZE+1;" is correct, 
but why not make it more readable and easy to understand

fix memory leak when rewrite config file

make replication tests more stable on slow machines

Potentially it is possible that we get interleaved writes, even if
serverLog() makes sure to write into a buffer and then use printf(), so
even this should be ok. However in general POSIX guarantees that writing
to the same file pointer object from multiple threads is safe. Anyway
currently we *reopen* the file at each call, but for the standard output
logging.

The logging functions actually also access global configuration while
performing the log (for instance in order to check the log level, the
log filename and so forth), however dunring the I/O threads execution
we cannot alter such shared state in any way.