Implement igbinary support
From http://opensource.dynamoid.com/ :
"Igbinary is a drop in replacement for the standard PHP serializer. Instead of time and space consuming textual representation, igbinary stores PHP data structures in a compact binary form. Savings are significant when using memcached or similar memory based storages for serialized data."
We should support igbinary and take advantage of it if it is installed.
[+FEATURE] FLOW3 (Cache): Implement igbinary support
This changeset adds support for the serialization accelerator
igbinary. If the igbinary extension is loaded, the VariableFrontend
of the cache framework will use its serialize() and unserialize()
functions instead of the PHP built-in variants.
Depending on the amount and nature of data, this speeds up cache
serialization by about 100%.