use "IPv6" and "IPv4" in strings as these are the official spellings and make ParseNetwork() in netbase.cpp case-insensitive

src/init.cpp

@@ -192,7 +192,7 @@ bool AppInit2(int argc, char* argv[])
             "  -timeout=<n>     \t  "   + _("Specify connection timeout (in milliseconds)") + "\n" +
             "  -proxy=<ip:port> \t  "   + _("Connect through socks proxy") + "\n" +
             "  -socks=<n>       \t  "   + _("Select the version of socks proxy to use (4 or 5, 5 is default)") + "\n" +
-            "  -noproxy=<net>   \t  "   + _("Do not use proxy for connections to network net (ipv4 or ipv6)") + "\n" +
+            "  -noproxy=<net>   \t  "   + _("Do not use proxy for connections to network <net> (IPv4 or IPv6)") + "\n" +
             "  -dns             \t  "   + _("Allow DNS lookups for -addnode, -seednode and -connect") + "\n" +
             "  -proxydns        \t  "   + _("Pass DNS requests to (SOCKS5) proxy") + "\n" +
             "  -port=<port>     \t\t  " + _("Listen for connections on <port> (default: 8333 or testnet: 18333)") + "\n" +
@@ -201,7 +201,7 @@ bool AppInit2(int argc, char* argv[])
             "  -connect=<ip>    \t\t  " + _("Connect only to the specified node") + "\n" +
             "  -seednode=<ip>   \t\t  " + _("Connect to a node to retrieve peer addresses, and disconnect") + "\n" +
             "  -externalip=<ip> \t  "   + _("Specify your own public address") + "\n" +
-            "  -blocknet=<net>  \t  "   + _("Do not connect to addresses in network net (ipv4, ipv6)") + "\n" +
+            "  -blocknet=<net>  \t  "   + _("Do not connect to addresses in network <net> (IPv4 or IPv6)") + "\n" +
             "  -discover        \t  "   + _("Try to discover public IP address (default: 1)") + "\n" +
             "  -irc             \t  "   + _("Find peers using internet relay chat (default: 0)") + "\n" +
             "  -listen          \t  "   + _("Accept connections from outside (default: 1)") + "\n" +

src/net.cpp

@@ -1796,7 +1796,7 @@ void static Discover()
                 struct sockaddr_in* s4 = (struct sockaddr_in*)(ifa->ifa_addr);
                 CNetAddr addr(s4->sin_addr);
                 if (AddLocal(addr, LOCAL_IF))
-                    printf("ipv4 %s: %s\n", ifa->ifa_name, addr.ToString().c_str());
+                    printf("IPv4 %s: %s\n", ifa->ifa_name, addr.ToString().c_str());
             }
 #ifdef USE_IPV6
             else if (ifa->ifa_addr->sa_family == AF_INET6)
@@ -1804,7 +1804,7 @@ void static Discover()
                 struct sockaddr_in6* s6 = (struct sockaddr_in6*)(ifa->ifa_addr);
                 CNetAddr addr(s6->sin6_addr);
                 if (AddLocal(addr, LOCAL_IF))
-                    printf("ipv6 %s: %s\n", ifa->ifa_name, addr.ToString().c_str());
+                    printf("IPv6 %s: %s\n", ifa->ifa_name, addr.ToString().c_str());
             }
 #endif
         }

src/netbase.cpp

@@ -11,6 +11,7 @@
 #endif
 
 #include "strlcpy.h"
+#include <boost/algorithm/string/case_conv.hpp> // for to_lower()
 
 using namespace std;
 
@@ -27,6 +28,7 @@ static bool vfNoProxy[NET_MAX] = {};
 static const unsigned char pchIPv4[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff };
 
 enum Network ParseNetwork(std::string net) {
+    boost::to_lower(net);
     if (net == "ipv4") return NET_IPV4;
     if (net == "ipv6") return NET_IPV6;
     if (net == "tor")  return NET_TOR;