datapath-windows: Add temporary files to gitignore.

Github Issue: #12

Reported-by: Alin Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Saurabh Shah <ssaurabh@vmware.com>
Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>