Add basic Collectable::isGarbage() and Collectable::setGarbage() docs on behalf of krakjoe

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@334849 c90b9560-bf6c-de11-be94-00142212c4b1
Update Collectable::isGarbage() and Collectable::setGarbage() descriptions

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@334850 c90b9560-bf6c-de11-be94-00142212c4b1
remaining docs for Collectable

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@334851 c90b9560-bf6c-de11-be94-00142212c4b1