Phalcon\Http\Request Optimizations

  * get raw request body from `SG(request_info).raw_post_data`, not via PHP streams;
  * faster getMethod();
  * fast path in isMETHOD() — do not call getMethod() if the calling class is Phalcon\Http\Request
  * optimize getHeaders()
  * optimize _getQualityHeader()
  * optimize _getBestQuality()