* replication hooks: role change, master link status, replica online/offline
* persistence hooks: saving, loading, loading progress
* misc hooks: cron loop, shutdown, module loaded/unloaded
* change the way hooks test work, and add tests for all of the above
startLoading() now gets flag indicating what is loaded.
stopLoading() now gets an indication of success or failure.
adding startSaving() and stopSaving() with similar args and role.
Some commands would want to open a key without touching it's LRU/LFU
similarly to the OBJECT or DEBUG command do.
Other commands may want to implement logic similar to what RESTORE
does (and in the future MIGRATE) and get/set the LRU or LFU.
Adding a test for coverage for RM_Call in a new "misc" unit
to be used for various short simple tests
also solves compilation warnings in redismodule.h and fork.c
As we know if a module exports module-side data types,
unload it is not allowed. This rule is the same with
blocked clients in module, because we use background
threads to implement module blocked clients, and it's
not safe to unload a module if there are background
threads running. So it's necessary to check if any
blocked clients running in this module when unload it.
Moreover, after that we can ensure that if no modules,
then no module blocked clients even module unloaded.
So, we can call moduleHandleBlockedClients only when
we have installed modules.
Calling a module hook callback may result in callback operations in turn
triggering other events the module is subscribed too. We don't want to
trigger those, it's unsafe and quite confusing, and to do it correcly we
would need to maintain an event list: quite a more complex
implementation.
* Introduce a connection abstraction layer for all socket operations and
integrate it across the code base.
* Provide an optional TLS connections implementation based on OpenSSL.
* Pull a newer version of hiredis with TLS support.
* Tests, redis-cli updates for TLS support.
