Simplify php_v8js_weak_object_callback.
Simplify php_v8js_weak_object_callback.

This also fixes a leak in the `object_dom` testcase, where the DOM extension
returns an object with refcnt 1 but object_store refcnt 2, causing
READY_TO_DESTROY to return false.  Don't try to be fancy, just use the
standard PHP destructor.

rosmo/v8js,php/pecl-languages-v8js,dayed/v8js,dayed/v8js,phpv8/v8js,rosmo/v8js,dayed/v8js,uniconstructor/v8js,php/pecl-languages-v8js,stesie/v8js,stesie/v8js,stesie/v8js,stesie/v8js,ABaldwinHunter/v8js-clone,preillyme/v8js,preillyme/v8js,phpv8/v8js,ABaldwinHunter/v8js-clone,zzhh9857/v8js,uniconstructor/v8js,dayed/v8js,preillyme/v8js,zzhh9857/v8js,phpv8/v8js,rosmo/v8js,ABaldwinHunter/v8js-clone,zzhh9857/v8js,ABaldwinHunter/v8js-clone,uniconstructor/v8js,zzhh9857/v8js,rosmo/v8js,uniconstructor/v8js,preillyme/v8js,php/pecl-languages-v8js,php/pecl-languages-v8js