Verify tags used in the gallery shortcode.



git-svn-id: http://core.svn.wordpress.org/trunk@23316 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Explicitly set last_changed to 1 instead of the result of wp_cache_set(). Avoids ambiguity and works with cache backends that return void instead of boolean.

see #23167


git-svn-id: http://core.svn.wordpress.org/trunk@23319 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Avoid the appearance of a magic number.

Props nacin
see #23167


git-svn-id: http://core.svn.wordpress.org/trunk@23320 1a063a9b-81f0-0310-95a4-ce76da25c4cd