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.

This bug affected RM_StringToLongDouble and HINCRBYFLOAT.
I added tests for both cases.

Main changes:
1. Fixed string2ld to fail if string contains \0 in the middle
2. Use string2ld in getLongDoubleFromObject - No point of
   having duplicated code here

The two changes above broke RM_SaveLongDouble/RM_LoadLongDouble
because the long double string was saved with length+1 (An innocent
mistake, but it's actually a bug - The length passed to
RM_SaveLongDouble should not include the last \0).

If a blocked module client times-out (or disconnects, unblocked
by CLIENT command, etc.) we need to call moduleUnblockClient
in order to free memory allocated by the module sub-system
and blocked-client private data

Other changes:
Made blockedonkeys.tcl tests a bit more aggressive in order
to smoke-out potential memory leaks

So error message `ERR only (P)SUBSCRIBE / (P)UNSUBSCRIBE / PING / QUIT allowed in this context` will become
`ERR 'get' command submitted, but only (P)SUBSCRIBE / (P)UNSUBSCRIBE / PING / QUIT allowed in this context`