- Implemented APC caching support since eaccelerator is not compatible
  with HPHP and although we support memcached, we do not use it on live.
- Replaced instances of create_function_cached with php anonymous
  functions. This bumps the PHP version requirement to 5.3, but it
  allows the code to work with HPHP, since dynamic function generation
  is replaced with staticly analyzable functions. This also removes a
  horrible, terrible hack in Textile.php which was storing the current
  instance of the Textile class being processed as a static variable so
  that it could be accessed by anonymous functions.
- Replaced occurrences of assert with log_assert.
- When running under HPHP, IA_HPHP_ENV is defined and is used to bypass
  some incompatible code (redundant ini configuration checks).
- Fixed some includes that were dependent on the working directory being
  www/
- Included a sample HPHP configuration file and a Makefile with
  compilation commands.