Increase the internal hash queue head count from 128 to 32768.
The hash queue is used for gathering and verifying lists, and the
original count of 128 may be overwhelmed if a list is extremely
large.  For example, on a 256GB system with 192GB of free pages,
the "kmem -f" command takes hours to complete; with this patch,
the time is reduced to a few minutes.  In addition, a new command
line option "--hash <count>" has been added to allow a user to
override the default hash queue head count of 32768.
(anderson@redhat.com)