Document --force-trojan as available on _WIN32
Fixes #277 (closed).
The alternative, if Trojan binary execution does need to be disabled on _WIN32
platforms, would be to guard all code related to force-trojan
and vpninfo->trojan_interval
with #ifndef _WIN32
. Who can tell what the intent was?
Edited by Dimitri Papadopoulos Orfanos