This is my current futex patchset against BK-curr.  It mostly includes
must-have crash/correctness fixes from Martin Wirth, tested and reworked
somewhat by myself:

 - crash fix: futex_close did not detach from the vcache. Detach cleanups.
   (Martin Wirth)

 - memory leak fix: forgotten put_page() in a rare path in __pin_page().
   (Martin Wirth)

 - crash fix: do not do any quickcheck in unqueue_me(). (Martin, me)

 - correctness fix: the fastpath in __pin_page() now handles reserved
   pages the same way get_user_pages() does. (Martin Wirth)

 - queueing improvement: __attach_vcache() now uses list_add_tail() to
   avoid the reversal of the futex queue if a COW happens. (Martin Wirth)

 - simplified alignment check in sys_futex. (Martin Wirth)

 - comment fix: make it clear how the vcache hash quickcheck works. (me)