* Adds an indirection to every allocation/deallocation to allow users to
plug in ones of their choosing (use custom functions, jemalloc, etc).
* Gracefully handle OOM everywhere in hiredis. This should make it possible
for users of the library to have more flexibility in how they handle such situations.
* Changes `redisReaderTask->elements` from an `int` to a `long long` to prevent
a possible overflow when transferring the task elements into a `redisReply`.
* Adds a configurable `max elements` member to `redisReader` that defaults to
2^32 - 1. This can be set to "unlimited" by setting the value to zero.
