Display unknown commands received.

src/main.cpp

@@ -4041,6 +4041,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
     else
     {
         // Ignore unknown commands for extensibility
+        LogPrint("net", "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->id);
     }