Description:
------------
This function could be similar to C signal() function (http://www.gnu.org/software/libc/manual/html_node/Basic-Signal-Handling.html) and return the previous value of the signal handler for passed signal, or false on error. This can be helpfull when you need to restore previous handler

Test script:
---------------
<?php
declare(ticks = 1);

function sig_handler($signo)
{

     switch ($signo) {
         case SIGTERM:
             exit;
             break;
         default:
     }

}

// this will return previous handler for SIGTERM signal
$previous_handler = pcntl_signal(SIGTERM, "sig_handler");

// restore previous handler
$previous_handler = pcntl_signal(SIGTERM, $previous_handler);

Expected result:
----------------
function pcntl_signal() returns previous value of the signal handler for passed signal on success or FALSE on failure

Actual result:
--------------
function pcntl_signal() returns TRUE on success or FALSE on failure