be more tolerant to detect outdated blockchain.

the main problem with running libtorrent with an outdated blockchain is to
refuse posts that are signed by new users. given this is only a temporary
state (and most of users are older than a day anyway) it is better to
be more tolerant instead of freezing up everything.

src/twister.cpp

@@ -425,7 +425,7 @@ void ThreadWaitExtIP()
 bool isBlockChainUptodate() {
     if( !pindexBest )
         return false;
-    return (pindexBest->GetBlockTime() > GetTime() - 2 * 60 * 60);
+    return (pindexBest->GetBlockTime() > GetTime() - 24 * 60 * 60);
 }
 
 bool yes(libtorrent::torrent_status const&)