Uthernet II: add virtual DNS feature (PR #1097)

Uthernet II: add extended feature to virtualise DNS requests.
. This allows pure TCP/UDP sockets to run *without* MACRAW requests (and so without libpcap).
. Raw sockets will not work.
. Add configuration for Virtual DNS.
libpcap: ensure all functions check if the library is loaded before using it.
Uthernet 1: do NOT overwrite tfe_cannot_use as it should only reflect the availability of npcap on *this* system.
Add Copyright notice, and mention Virtual DNS in html.

source/Configuration/PropertySheetHelper.cpp

@@ -33,6 +33,8 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #include "../Log.h"
 #include "../Registry.h"
 #include "../SaveState.h"
+#include "../Interface.h"
+#include "../Uthernet2.h"
 #include "../Tfe/PCapBackend.h"
 
 /*
@@ -336,7 +338,8 @@ void CPropertySheetHelper::ApplyNewConfig(const CConfigNeedingRestart& ConfigNew
 		SetSlot(slot, ConfigNew.m_Slot[slot]);
 
 	// unconditionally save it, as the previous SetSlot might have removed the setting
-	PCapBackend::tfe_SetRegistryInterface(slot, ConfigNew.m_tfeInterface);
+	PCapBackend::SetRegistryInterface(slot, ConfigNew.m_tfeInterface);
+	Uthernet2::SetRegistryVirtualDNS(slot, ConfigNew.m_tfeVirtualDNS);
 
 	slot = SLOT4;
 	if (CONFIG_CHANGED_LOCAL(m_Slot[slot]))
@@ -455,6 +458,9 @@ bool CPropertySheetHelper::HardwareConfigChanged(HWND hWnd)
 		if (CONFIG_CHANGED(m_tfeInterface))
 			strMsgMain += ". Uthernet interface has changed\n";
 
+		if (CONFIG_CHANGED(m_tfeVirtualDNS))
+			strMsgMain += ". Uthernet Virtual DNS has changed\n";
+
 		if (CONFIG_CHANGED(m_Slot[SLOT4]))
 			strMsgMain += GetSlot(SLOT4);