Fix for #270 to allow subnets

This seems to work as expected and allows CIDR, subnet, and single IP while rejecting IPs out of range.

src/stratum.cpp

@@ -123,10 +123,8 @@ namespace { // better to use anonymous namespace for helper routines
         if (mapMultiArgs.count("-stratumallowip")) {
             const std::vector<std::string>& vAllow = mapMultiArgs["-stratumallowip"];
             for(const std::string& strAllow : vAllow) {
-    		CNetAddr netaddr;
-		// todo: v6
-    		LookupHost(strAllow.c_str(), netaddr, false);
-                CSubNet subnet(netaddr);
+		CSubNet subnet;
+    		LookupSubNet(strAllow.c_str(), subnet);
                 if (!subnet.IsValid()) {
                     uiInterface.ThreadSafeMessageBox(
                         strprintf("Invalid -stratumallowip subnet specification: %s. Valid are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24).", strAllow),