Given a choice between several available CPUs (unlinked) on which
to schedule a task, let the scheduler select the CPU closest to
where that task was previously scheduled.  Hopefully, this will
reduce cache migration penalties.

TODO: If a lower-priority task must be preempted and there are several
scheduled tasks with the same low priority, then preempt the closest.

The next owner of a FMLP-protected resource is dequeued from
the FMLP FIFO queue by unlock() (when the resource is freed by
the previous owner) instead of performing the dequeue by the next
owner immediately after it has been woken up.

This simplifies the code a little bit and also reduces potential
spinlock contention.

Inspired by the existing C-EDF code, this generic version will build
clusters of CPUs based on a given cache level.

Make the cluster size configuration in C-EDF generic so that it can be
used by other clustered schedulers.

Since we don't expect to trace more than one lock type at a time,
having protocol-specific trace points is not required.

As Glenn pointed out, it is useful for some protocols (e.g.,
k-exclusion protocols) to know the userspace configuration at object
creation time. This patch changes the fdso API to pass the parameter
to the object constructor, which is then in turn passed to the lock
allocater. The return code from the lock allocater is passed to
userspace in return.

This also fixes some null pointer dereferences in the FDSO code found
by the test suite in liblitmus.

Implement the partitioned FMLP with priority boosting based on the
generic lock API.

While we are at it, simplify edf_higher_prio() a bit.