Description:
------------
Using the is_callable function to check the existence of a method using a string 
identifier for the class fails to work as expected when the method name is the 
same as the class name.

Normally, I would use method_exists(), but it doesn't account for whether or not 
the method is accessible.

This bug does not seem to occur on 5.2.5 (tested on codepad).

My exact PHP version is "5.4.3-4~precise+1"

Test script:
---------------
<?php
class Test
{
   public function test ()
   {
   }
}

var_dump (is_callable (array ('Test', 'test')));

Expected result:
----------------
bool(true)

Actual result:
--------------
bool(false)