Windows: return ENOMEM from cm_BPlus functions on malloc failure

Windows: return ENOMEM from cm_BPlus functions on malloc failure

There are several cm_BPlus functions that do not return
an error code on malloc failure.

LICENSE MIT

Change-Id: I3a3d78cc6d6844c78e51fa81ebf330f5af88a7a5
Reviewed-on: http://gerrit.openafs.org/900
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Reviewed-by: Asanka Herath <asanka@secure-endpoints.com>
Tested-by: Asanka Herath <asanka@secure-endpoints.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>