- Patch #29002 by Neil: list_themes() currently returns all themes, not just enabled themes. This functionality is only used in one place- configuration for disabled themes. These configuration pages can be removed with a usability improvement since you shouldn't be able to configure things which are disabled. Additionally, this allows us to remove some extra logic in system_user(). And it it more consistent with the module API which only lists enabled modules.

list_themes() sorts the results by name. This uses filesort in MySQL since there aren't any indexes. Sorting is not used except in system_user(). This one use can be handled with ksort since it is not often executed (only on the user edit screen when multiple themes are enabled).

And a one line fix to remove a variable in system_user() is in here too.