This helps in avoiding multiple definition of this variable, its also
defined globally in sds.c
Signed-off-by: NKhem Raj <raj.khem@gmail.com>

Signed-off-by: Nlifubang <lifubang@acmcoder.com>

1. Call emptyDb even in case of diskless-load: We want modules
   to get the same FLUSHDB event as disk-based replication.
2. Do not fire any module events when flushing the backups array.
3. Delete redundant call to signalFlushedDb (Called from emptyDb).

Signed-off-by: Nlifubang <lifubang@acmcoder.com>

Because "keymiss" is "special" compared to the rest of
the notifications (Trying not to break existing apps
using the 'A' format for notifications)

Also updated redis.conf and module.c docs

SELECT, and HELLO are commands that may be executed by the client
as soon as it connects, there's no reason to block them, preventing the
client from doing the rest of his sequence (which might just be INFO or
CONFIG, etc).

MONITOR, DEBUG, SLOWLOG, TIME, LASTSAVE are all non-data accessing
commands, which there's no reason to block.

the warning condition was if usage > limit (saying it'll cause eviction
or oom), but in fact the eviction and oom depends on used minus slave
buffers.

other than fixing the condition, i add info about the current usage and
limit, which may be useful when looking at the log.

currently there's no bug since the flags these functions handle are
always lower than 32bit, but still better fix the type to prevent future
bugs.

using panic rather than exit means you get s stack trace of the code
path that experianced the error, and possibly other info.

this function possibly iterates on the module list

replicationUnsetMaster can be called from other places, not just
replicaofCOmmand, and all of these need to restart AOF

althouh in theory, users can do BGREWRITEAOF even if aof is disabled, i
suppose it is more common that the scheduled flag is set by either
startAppendOnly, of a failed initial AOFRW fork (AOF_WAIT_REWRITE)

1. server.repl_no_slaves_since can be set when a MONITOR client disconnects
2. c->repl_ack_time can be set by a newline from a MONITOR client
3. Improved comments

We noticed that the error replies for the generic mechanism for enums
are very verbose for config file parsing, but not for config set
command.

instead of replicating this code, i did a small refactoring to share
code between CONFIG SET and config file parsing.

and also renamed the enum group functions to be consistent with the
naming of other types.