Windows: Use a timestamp for the minidump filename

Windows: Use a timestamp for the minidump filename

Set the name of the minidump file to :
%TMP%\afsd-<yyyy>-<mm>-<dd>-<hh>_<mm>_<ss>.dmp

This prevents new minidump files from overwriting older ones.

Change-Id: I057963bedf618eb23720f17d62c8473790569273
Reviewed-on: http://gerrit.openafs.org/1633
Reviewed-by: Asanka Herath <asanka@secure-endpoints.com>
Tested-by: Asanka Herath <asanka@secure-endpoints.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>