User system doesn't communicate with modules about roles: add user roles API

This patch introduces hook_user_role_delete, a hook that would allow modules to act when a use role is deleted.

The hook is implemented in filter.module and block.module.

I am marking this critical, to get some attention before the freeze, as this introduces a new hook (API), .

but shouldn't we have hooks for adding and updating too -- for consistency?

Currently, I can't see a case when a module might need to act when a role is updated (role name changed), but might be later. So, yes, for consistency.

This patch adds:

- API functions to manipulate user roles: user_role_load($rid), user_role_save($role), user_role_delete($role)
- hooks hook_user_role_insert($role), hook_user_role_update($role), hook_user_role_delete($role)
- Implementation of hook_user_role_delete() in core modules filter.momdule and block.mdoule

tagging

Tagging.

Ok, I will take that issue, marking this as duplicate.