Added feature to start FreshClam & Clamd as Windows services
Special thanks to Gianluigi Tiesi for allowing us to integrate this
feature from ClamWin directly into ClamAV.
Added internal --service-mode option for FreshClam and ClamD
This is used when Windows starts FreshClam or ClamD as a service so
that they will register with the service manager.
Code found in service.c.