Description:
------------
Using GearmanJob::setReturn will cause the worker to segfault and send a return code of GEARMAN_WORK_FAIL.

Reproduce code:
---------------
<?php
$gmworker= new GearmanWorker();
$gmworker->addServer();
$gmworker->addFunction("func", "func");

while($gmworker->work());

function func($job)
{
    $job->setReturn(GEARMAN_SUCCESS);
}
?>

Expected result:
----------------
A return code of GEARMAN_SUCCESS sent back to the client.

Actual result:
--------------
A return code of GEARMAN_WORK_FAIL is sent to the client and the worker segfaults.

Backtrace:
Starting program: /usr/local/php5.3.3/bin/php worker.php
[Thread debugging using libthread_db enabled]

Program received signal SIGSEGV, Segmentation fault.
0x00000000008a1f4a in zend_object_store_get_object (zobject=0x0)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_objects_API.c:270
270             zend_object_handle handle = Z_OBJ_HANDLE_P(zobject);
(gdb) bt
#0  0x00000000008a1f4a in zend_object_store_get_object (zobject=0x0)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_objects_API.c:270
#1  0x00002aaaaeb20ec7 in zif_gearman_job_set_return (ht=1,
    return_value=0x114b0c0, return_value_ptr=0x0, this_ptr=0x114ad60,
    return_value_used=0)
    at /home/hradtke/projects/php/src/pecl/gearman/trunk/php_gearman.c:1651
#2  0x00000000008a4706 in execute_internal (execute_data_ptr=0x2aaaaf5802d8,
    return_value_used=0)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_execute.c:1261
#3  0x00002aaaae6b4f4a in xdebug_execute_internal (
    current_execute_data=0x2aaaaf5802d8, return_value_used=0)
    at /home/hradtke/tmp/xdebug-2.1.0/xdebug.c:1339
#4  0x00000000008a589a in zend_do_fcall_common_helper_SPEC (
    execute_data=0x2aaaaf5802d8)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_vm_execute.h:318
#5  0x00000000008a6662 in ZEND_DO_FCALL_BY_NAME_SPEC_HANDLER (
    execute_data=0x2aaaaf5802d8)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_vm_execute.h:421
#6  0x00000000008a4a53 in execute (op_array=0x116cab0)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_vm_execute.h:107
#7  0x00002aaaae6b4bc5 in xdebug_execute (op_array=0x116cab0)
    at /home/hradtke/tmp/xdebug-2.1.0/xdebug.c:1272
#8  0x0000000000864346 in zend_call_function (fci=0x7fffffffbb90,
    fci_cache=0x7fffffffbb60)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_execute_API.c:963
#9  0x00002aaaaeb26a40 in _php_worker_function_callback (job=0x114a860,
    context=0x114ac70, result_size=0x114a110, ret_ptr=0x7fffffffbc54)
    at /home/hradtke/projects/php/src/pecl/gearman/trunk/php_gearman.c:3434
#10 0x0000003fd34067c8 in gearman_worker_work (worker=0x114a0f8)
    at libgearman/worker.c:829
#11 0x00002aaaaeb26fd9 in zif_gearman_worker_work (ht=0,
    return_value=0x114ace8, return_value_ptr=0x0, this_ptr=0x1146220,
    return_value_used=1)
    at /home/hradtke/projects/php/src/pecl/gearman/trunk/php_gearman.c:3537
#12 0x00000000008a4706 in execute_internal (execute_data_ptr=0x2aaaaf580090,
    return_value_used=1)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_execute.c:1261
#13 0x00002aaaae6b4f4a in xdebug_execute_internal (
    current_execute_data=0x2aaaaf580090, return_value_used=1)
    at /home/hradtke/tmp/xdebug-2.1.0/xdebug.c:1339
#14 0x00000000008a589a in zend_do_fcall_common_helper_SPEC (
    execute_data=0x2aaaaf580090)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_vm_execute.h:318
#15 0x00000000008a6662 in ZEND_DO_FCALL_BY_NAME_SPEC_HANDLER (
    execute_data=0x2aaaaf580090)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_vm_execute.h:421
#16 0x00000000008a4a53 in execute (op_array=0x1146ee0)
    at /home/hradtke/tmp/php-5.3.3/Zend/zend_vm_execute.h:107
#17 0x00002aaaae6b4bc5 in xdebug_execute (op_array=0x1146ee0)
    at /home/hradtke/tmp/xdebug-2.1.0/xdebug.c:1272
#18 0x000000000087449b in zend_execute_scripts (type=8, retval=0x0,
    file_count=3) at /home/hradtke/tmp/php-5.3.3/Zend/zend.c:1194
#19 0x00000000007fe9f3 in php_execute_script (primary_file=0x7fffffffe620)
    at /home/hradtke/tmp/php-5.3.3/main/main.c:2260
---Type <return> to continue, or q <return> to quit---
#20 0x0000000000963752 in main (argc=2, argv=0x7fffffffe878)
    at /home/hradtke/tmp/php-5.3.3/sapi/cli/php_cli.c:1192