NotifyBlockTip signal: switch from hash (uint256) to CBlockIndex*

- also adds a boolean for indication if the tip update was happening during initial sync
- emit notification also during initial sync

src/init.cpp

@@ -515,11 +515,14 @@ std::string LicenseInfo()
            "\n";
 }
 
-static void BlockNotifyCallback(const uint256& hashNewTip)
+static void BlockNotifyCallback(bool initialSync, const CBlockIndex *pBlockIndex)
 {
+    if (initialSync || !pBlockIndex)
+        return;
+
     std::string strCmd = GetArg("-blocknotify", "");
 
-    boost::replace_all(strCmd, "%s", hashNewTip.GetHex());
+    boost::replace_all(strCmd, "%s", pBlockIndex->GetBlockHash().GetHex());
     boost::thread t(runCommand, strCmd); // thread runs free
 }