Set WP_Theme::scandir()'s default depth to 0 (flat), as intended. Cache...

Set WP_Theme::scandir()'s default depth to 0 (flat), as intended. Cache untranslated page template names. Properly merge in a parent theme's templates when dealing with cached values. Always look one level deep for WP_Theme->get_files() regardless of file type. see #20103. see #11216.



git-svn-id: https://core.svn.wordpress.org/trunk@20327 1a063a9b-81f0-0310-95a4-ce76da25c4cd