[netgroupman] Add GetMappedAS() and GetGroup()

These currently call through to the CNetAddr methods. The logic will be moved in a future commit.

src/netgroup.h

@@ -5,6 +5,8 @@
 #ifndef BITCOIN_NETGROUP_H
 #define BITCOIN_NETGROUP_H
 
+#include <netaddress.h>
+
 #include <vector>
 
 /**
@@ -20,6 +22,10 @@ public:
      * exists, since the data is const. */
     const std::vector<bool>& GetAsmap() const { return m_asmap; }
 
+    std::vector<unsigned char> GetGroup(const CNetAddr& address) const;
+
+    uint32_t GetMappedAS(const CNetAddr& address) const;
+
 private:
     /** Compressed IP->ASN mapping, loaded from a file when a node starts.
      *