Added CanBeDeleted class, which implements a timeout function. It is
used to make sure that (in this case) the NewsManager thread does not
need the file manager anymore when stk exists (which can only happen
on very very quick exists, and slow downloads). This avoids a potential
crash that the NewsManager thread could access the file manager after
the file manager was deleted.
Added a 'non-abortable' flag to the signout request. Re-enabled cancelling
ongoing downloads to allow for a quicker exit of STK.
Merge branch 'master' of github.com:supertuxkart/stk-code
Wait for request_manager to be ready to be deleted (i.e. current request
have been properly aborted, and sign out done). Also shut down more of
STK after signaling the request manager to shut down, so that the user does
not notice the time for the sign out. Also added docs.