Adjust OC_Filesystem use in hooks to string, so the class is loaded as late as possible

apps/files_versions/appinfo/app.php

@@ -6,4 +6,4 @@ OCP\App::registerAdmin('files_versions', 'settings');
 OCP\Util::addscript('files_versions', 'versions');
 
 // Listen to write signals
-OCP\Util::connectHook(OC_Filesystem::CLASSNAME, OC_Filesystem::signal_post_write, "OCA_Versions\Storage", "write_hook");
+OCP\Util::connectHook('OC_Filesystem', 'post_write', "OCA_Versions\Storage", "write_hook");

apps/gallery/lib/hooks_handlers.php

@@ -21,7 +21,7 @@
 * 
 */
 
-OCP\Util::connectHook(OC_Filesystem::CLASSNAME, OC_Filesystem::signal_delete, "OC_Gallery_Hooks_Handlers", "removePhoto");
+OCP\Util::connectHook('OC_Filesystem', 'delete', "OC_Gallery_Hooks_Handlers", "removePhoto");
 //OCP\Util::connectHook(OC_Filesystem::CLASSNAME, OC_Filesystem::signal_post_rename, "OC_Gallery_Hooks_Handlers", "renamePhoto");
 
 require_once(OC::$CLASSPATH['Pictures_Managers']);