[thrift] PHP generator: extension support

[thrift] PHP generator: extension support

Summary: Adds php code generation to take advantage of the php
  'thrift_protocol' extension (currently for deserialization only)

  Requires you to swap your protocol for a TBinaryProtocolAccelerated
  (which just inherits TBinaryProtocol without actually adding any
  new functionality) and that you use a TFramedTransport or wrap your
  transport in a TBufferedTransport.

  TBinaryProtocolAccelerated is currently only in tfb/www/lib (or will
  be momentarily).

Reviewed By: mcslee
Test Plan: synapse_feed uses this in my sandbox, works fine
Revert: svn

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@665313 13f79535-47bb-0310-9956-ffa450edef68