Cache_redis: Adding serialization support.
Cache_redis: AND -> && correction, srrict in_array() check.
Cache_redis: Strinct array_search() for now.
Cache_redis, delete() method: Removing code for updating the internal cache, it is useless.
Cache_redis, Hardcoded name for the auxilary Redis set - '_ci_redis_serialized'.
Cache_redis, delete() method: Bringing back a line of code.
Cache_redis, delete() method: Try to remove a key from Redis auxilary set only when the corresponding value is really deleted.
Cache_redis, save() method: An optimization, moving sRemove call.
Cache_redis: Refactoring if delete() method.
Cache_redis: Polishing.
Cache_redis: Optimizations.
Cache_redis: A code-styling correction..
Merge pull request #3186 from ivantcholakov/feature/cache-redis-serialization

Cache_redis: Adding serialization support.