Futexes functionalities and improvements

Hi Andrew,

	This is a re-send of a series of patches concerning futexes (here after is a short description)

	Could you consider them for inclusion in -mm tree ?

	All of them have already been discussed in January and have already been included in -rt for a
while. I think that we agreed to potentially include them in the -mm tree.

	Ulrich is specially interested by sys_futex64.

There are:
    * futex uses prio list : allows RT-threads to be woken in priority order
instead of FIFO order.
    * futex_wait uses hrtimer : allows the use of finer timer resolution.
    * futex_requeue_pi functionality : allows use of requeue optimization for
PI-mutexes/PI-futexes.
    * futex64 syscall : allows use of 64-bit futexes instead of 32-bit. 


Note: it does not inlcude the fix "PI state locking fix" sent yesterday by Ingo.

Thanks,

-- 
Pierre