Fix AOF bug: expire could be removed from key on AOF rewrite.

There was a race condition in the AOF rewrite code that, with bad enough
timing, could cause a volatile key just about to expire to be turned
into a non-volatile key. The bug was never reported to cause actualy
issues, but was found analytically by an user in the Redis mailing list:

https://groups.google.com/forum/?fromgroups=#!topic/redis-db/Kvh2FAGK4Uk

This commit fixes issue #1079.
Reset masterauth if an empty string is configured.
CONFIG SET server.masterauth aesthetic change.

This is just to make the code exactly like the above instance used for
requirepass. No actual change nor the original code violated the Redis
coding style.
Added more info about 32 bit builds into README.
in 32bit machine, popcount don't work with a input string length up to 512 MB,
bitcount commant may return negtive integer with string length more than 256 MB
Test: various issues with the replication-4.tcl test fixed.

The test actually worked, but vars for master and slave were inverted
and sometimes used incorrectly.
redis-cli: help.h updated.
Binary safe dump of object content in redisLogObjectDebugInfo().
Allow writes from scripts called by AOF loading in read-only slaves.

This fixes issue #1163
Test: regression test for #1163.
Sentinel: parse new INFO replication output correctly.

Sentinel was not able to detect slaves when connected to a very recent
version of Redis master since a previos non-backward compatible change
to INFO broken the parsing of the slaves ip:port INFO output.

This fixes issue #1164
Redis 2.6.14
Fixed typo in 2.6.14 changelog. verison -> version.
Merge commit 'fetch_head' into viki

Conflicts:
	src/version.h