Make CNetAddr::GetHash() return an unsigned val.

This prevents an undefined operation in main.cpp, when shifting the hash value
left by 32 bits.
Shifting a signed int left into the sign bit is undefined in C++11.

src/main.cpp

@@ -2440,7 +2440,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
                     static uint256 hashSalt;
                     if (hashSalt == 0)
                         RAND_bytes((unsigned char*)&hashSalt, sizeof(hashSalt));
-                    int64 hashAddr = addr.GetHash();
+                    uint64 hashAddr = addr.GetHash();
                     uint256 hashRand = hashSalt ^ (hashAddr<<32) ^ ((GetTime()+hashAddr)/(24*60*60));
                     hashRand = Hash(BEGIN(hashRand), END(hashRand));
                     multimap<uint256, CNode*> mapMix;

src/netbase.cpp

@@ -820,10 +820,10 @@ std::vector<unsigned char> CNetAddr::GetGroup() const
     return vchRet;
 }
 
-int64 CNetAddr::GetHash() const
+uint64 CNetAddr::GetHash() const
 {
     uint256 hash = Hash(&ip[0], &ip[16]);
-    int64 nRet;
+    uint64 nRet;
     memcpy(&nRet, &hash, sizeof(nRet));
     return nRet;
 }

src/netbase.h

@@ -66,7 +66,7 @@ class CNetAddr
         std::string ToString() const;
         std::string ToStringIP() const;
         int GetByte(int n) const;
-        int64 GetHash() const;
+        uint64 GetHash() const;
         bool GetInAddr(struct in_addr* pipv4Addr) const;
         std::vector<unsigned char> GetGroup() const;
         int GetReachabilityFrom(const CNetAddr *paddrPartner = NULL) const;