Patch from Manfred Spraul <manfred@colorfullife.com>

Fixes the lock contention over file_list_lock by simply removing the unneeded
anon_list.  So filp allocation does not need to take a global lock any more.

The use of a spinlock to protect files_stat.nr_files is a bit awkward, but
the alternative is a custom sysctl handler, and isn't much more efficient
anyway.