Windows: record history of read lock threads

Windows: record history of read lock threads

Maintance an array of up to 32 reader threads that have
acquired a rwlock.  Use it for debugging when things go bad.

Reviewed-on: http://gerrit.openafs.org/5411
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit c9d655b9a6edf02fd92455961445f239f4667821)

Change-Id: Icab5ffc36e4c6245b7d0699596eca66a66bc9538
Reviewed-on: http://gerrit.openafs.org/6038
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>