Description:
------------
when i checking out the cURL header using CURLINFO_HEADER_OUT, the post data didn't show in the body.

Test script:
---------------
    $ch = curl_init();
    curl_setopt( $ch, CURLOPT_URL, 'http://www.google.com.hk/webhp?hl=zh-CN&sourceid=cnhp' );
    curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
    curl_setopt( $ch, CURLINFO_HEADER_OUT, true );
    curl_setopt( $ch, CURLOPT_POST, true );
    curl_setopt( $ch, CURLOPT_POSTFIELDS, http_build_query(array('a'=>'1','b'=>'2')));
    $response = curl_exec( $ch );

    var_dump( curl_getinfo( $ch, CURLINFO_HEADER_OUT ) );
    
    curl_close( $ch );
    unset( $ch );

Expected result:
----------------
POST /webhp?hl=zh-CN&sourceid=cnhp HTTP/1.1
Host: www.google.com.hk
Accept: */*
Content-Length: 7
Content-Type: application/x-www-form-urlencoded

a=1&b=2    // <- missing this

Actual result:
--------------
POST /webhp?hl=zh-CN&sourceid=cnhp HTTP/1.1
Host: www.google.com.hk
Accept: */*
Content-Length: 7
Content-Type: application/x-www-form-urlencoded