Windows: Use secure ctime and strncpy in afs_ctime

Windows: Use secure ctime and strncpy in afs_ctime

Microsoft compilers version 1500 and above provide secure
versions of ctime and strncpy.  Use them in afs_ctime.

Reviewed-on: http://gerrit.openafs.org/408
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Asanka Herath <asanka@secure-endpoints.com>
Reviewed-by: Asanka Herath <asanka@secure-endpoints.com>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>