Merge #13532: Log warning when deprecated network name 'tor' is used

9f8c54b1b5 Log warning message when deprecated network name 'tor' is used (e.g. option onlynet=tor) (wodry)

Pull request description:

  As @laanwj mentioned [here](https://github.com/bitcoin/bitcoin/pull/13418#discussion_r197645385), using option `onlynet=tor` is deprecated.

  I think it would be good to give the user a depcreaction warning feedback, so users can switch to `onlynet=onion` so there is a perspective for removing the deprecated `tor` in the future to decrease confusion.

  Currently, users maybe just wonder that they can use a undocumented option, or they are not aware that they use a deprecated option.

  Alternatively for the log warning message, I think at least this deprecetaion should be documented in the source code in a comment for readers of the source code.

Tree-SHA512: f4889793cdd62a0a13353e13994ed50ca7d367fa9da9897ce909f86cf0b0ce6151b3c484c8e514b8ac332949c6bbc71001e06e918248a1089f73756bd4840602

src/netbase.cpp

@@ -41,7 +41,11 @@ 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" || net == "onion")  return NET_TOR;
+    if (net == "onion") return NET_TOR;
+    if (net == "tor") {
+        LogPrintf("Warning: net name 'tor' is deprecated and will be removed in the future. You should use 'onion' instead.\n");
+        return NET_TOR;
+    }
     return NET_UNROUTABLE;
 }