Add optional Sphinx SE plugin support to MySQL 5.5 and 5.6.
Intented as a clean implementation (replacement) of wip/mysql-sphinxse.

SphinxSE is MySQL storage engine which can be compiled into MySQL server 5.x
using its pluggable architecture. Despite the name, SphinxSE does not
actually store any data itself. It is actually a built-in client which
allows MySQL server to talk to searchd, run search queries, and obtain
search results. All indexing and searching happen outside MySQL.

See http://sphinxsearch.com/docs/current.html#sphinxse-overview

(fhajny)