Auto merge of #3263 - str4d:ibd-upstream-changes, r=bitcartel

InitialBlockDownload upstream changes

Cherry-picked from the following upstream PRs:

- bitcoin/bitcoin#7208
- bitcoin/bitcoin#8007
- bitcoin/bitcoin#9053
  - Excluding second commit (requires bitcoin/bitcoin#8865)
- bitcoin/bitcoin#10388

src/init.cpp

@@ -470,6 +470,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-limitfreerelay=<n>", strprintf("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default: %u)", 15));
         strUsage += HelpMessageOpt("-relaypriority", strprintf("Require high priority for relaying free or low-fee transactions (default: %u)", 0));
         strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf("Limit size of signature cache to <n> entries (default: %u)", 50000));
+        strUsage += HelpMessageOpt("-maxtipage=<n>", strprintf("Maximum tip age in seconds to consider node in initial block download (default: %u)", DEFAULT_MAX_TIP_AGE));
     }
     strUsage += HelpMessageOpt("-minrelaytxfee=<amt>", strprintf(_("Fees (in %s/kB) smaller than this are considered zero fee for relaying (default: %s)"),
         CURRENCY_UNIT, FormatMoney(::minRelayTxFee.GetFeePerK())));
@@ -1075,6 +1076,8 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     if (GetBoolArg("-peerbloomfilters", true))
         nLocalServices |= NODE_BLOOM;
 
+    nMaxTipAge = GetArg("-maxtipage", DEFAULT_MAX_TIP_AGE);
+
 #ifdef ENABLE_MINING
     if (mapArgs.count("-mineraddress")) {
         CTxDestination addr = DecodeDestination(mapArgs["-mineraddress"]);