[$] Rethinking the futex API

The Linux futex()system call is a bit of a strange beast. It is widely used to providelow-level synchronization support in user space, but there is no wrapperfor it in the GNU C Library. Its implementation was meant to be simple,but kernel developers have despaired at the complex beast that it hasbecome, and few dare to venture into that code. Recently, though, a neweffort has begun to rework futexes; it is limited to a new system-callinterface for now, but the plans go far beyond that.