Description:
------------
As per XHProf documentation, (http://mirror.facebook.net/facebook/xhprof/doc.html#include_funcs), "include", "include_once"/"require"/"require_once" operations are special cased.

----
For example, an 
  include "lib/common.php"; 
operation will get reported in XHProf as two function entries:

    * load::lib/common.php - This represents the work done by the interpreter to compile/load the file. [Note: If you are using a PHP opcode cache like APC, then the compile only happens on a cache miss in APC.]
    * run_init::lib/common.php - This represents initialization code executed at the file scope as a result of the include operation.
----

However, the implementation is currently only doing this special casing for include/include_once, but not require/ require_once.