Windows: Ensure consistency of error code mapping

Windows: Ensure consistency of error code mapping

For Windows, the error mapping table used throughout the system
is located in util/errmap_nt.h.   This table was incomplete and
WINNT/afsd/cm_utils.c added additional mapping locally.  Move
said error mapping to util/errmap_nt.h.

When including afs/unified_afs.h it must be done after including
afs/errmap_nt.h.   Otherwise, undefined errors are mapped to EIO
which should not be.

LICENSE MIT

Reviewed-on: http://gerrit.openafs.org/328
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>