set svn keywords for collectable/isgarbage.xml

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@334853 c90b9560-bf6c-de11-be94-00142212c4b1
space needed between </modifier> and <type>

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@334854 c90b9560-bf6c-de11-be94-00142212c4b1