Some simple formatting changes

Moved our ResultCallback define to the top (before function protos)
as well as moved PHP_REDIS_VERSION define to the very top of php_redis.h
OCD formatting changes
Introspection commands

Implemented various introspection/option commands for both Redis
and RedisCluster.

Commands implemented:

* getOption
* setOption
* _prefix
* _serialize
* _unserialize

With these implemented, we can properly test RedisCluster with things
like serialization and prefixing turned on.