sds.c: Correct some comments
sds.c/sdscatvprintf: set va_end to finish va_list cpy
sds.c: Correct two spelling mistakes in comments
override histfile from env - fixes #831 and copies #833
Add SENTINEL INFO-CACHE [masters...]

Sentinel queries the INFO from every master and from every replica of
every master.

We can cache the INFO results in Sentinel so Sentinel can be a single
place to quickly get all INFO output for an entire Sentinel monitoring
group.

This commit gives us SENTINEL INFO-CACHE in two forms:
  - SENTINEL INFO-CACHE — returns all masters and all replicas
  - SENTINEL INFO-CACHE master0 master1 ... masterN — vararg specify masters

Results are returned as a multibulk reply with two top-level entries
for each master.  The first entry for each master is the name of the master.
The second entry is a nested multibulk reply with the contents of INFO,
first for the master, then an additional entry for each of the
replicas.
zipmap.c: update comments above
redis-benchmark AUTH command to be discarded after the first send #2150
Fix implicit declaration of ioctl on Solaris
replaced // comments  #2150
bitops.c/redisPopcount: little optimization in loop
Mark diskless replication as experimental in redis.conf.
Mark PFCOUNT as read-only, even if not true.

PFCOUNT is technically speaking a write command, since the cached value
of the HLL is exposed in the data structure (design error, mea culpa), and
can be modified by PFCOUNT.

However if we flag PFCOUNT as "w", read only slaves can't execute the
command, which is a problem since there are environments where slaves
are used to scale PFCOUNT reads.

Nor it is possible to just prevent PFCOUNT to modify the data structure
in slaves, since without the cache we lose too much efficiency.

So while this commit allows slaves to create a temporary inconsistency
(the strings representing the HLLs in the master and slave can be
different in certain moments) it is actually harmless.

In the long run this should be probably fixed by turning the HLL into a
more opaque representation, for example by storing the cached value in
the part of the string which is not exposed (this should be possible
with SDS strings).
Over 80 chars comment trimmed in pfcountCommand().
Use exp format and more precision output for ZSCAN.

Ref: issue #2175
bitops.c/bitopCommand: skip short minlen for FAST PATH
Handle infinite explicitly in createStringObjectFromLongLong().
Regression test for issue #2175.
Don't show the ASCII logo if syslog is enabled.

Closes issue #1935.
Network bandwidth tracking + refactoring.

Track bandwidth used by clients and replication (but diskless
replication is not tracked since the actual transfer happens in the
child process).

This includes a refactoring that makes tracking new instantaneous
metrics simpler.
Check that tcp-backlog is matched by /proc/sys/net/core/somaxconn.