Windows: correct pthread_xxx_init semantics

Windows: correct pthread_xxx_init semantics

pthread lock and conditional initialization semantics
do not require that the lock structure be zeroed before
pthread_xxxx_init() functions are called.  Since the Windows
CriticalSection initialization does require that the memory
be zeroed, the pthread_xxxx_init() functions must zero the
memory just in case before performing the CriticalSection
initialization.

Change-Id: I61e78ca7cbc10f7d4144b8efcbb38f67bb8fd695
Reviewed-on: http://gerrit.openafs.org/3904
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>