viced (non atomic) refcount/more-threads

viced (non atomic) refcount/more-threads

Replace host-hold bitmap with reference counting, phase 1, not atomic.
Increase viced MAX_THREADS.

NOTE: This code has been tested on Centos 5.3 x86_64, on VMWare, 2 physical,
2 logical CPUs.

LICENSE BSD

Change-Id: Id62dcc786619dfd99e1a7b69a196bbaa0b45158c
Change-Id: I8ee2ec645402f02fdba0920815409b56172d393b
Reviewed-on: http://gerrit.openafs.org/268
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>