Allow interaction with PV49.

Remove unneeded include.

libethcore/BlockInfo.cpp

@@ -22,6 +22,7 @@
 #include <libdevcore/Common.h>
 #include <libdevcore/RLP.h>
 #include <libdevcrypto/TrieDB.h>
+#include <libethcore/CommonEth.h>
 #include "ProofOfWork.h"
 #include "Exceptions.h"
 #include "BlockInfo.h"
@@ -190,7 +191,7 @@ u256 BlockInfo::calculateDifficulty(BlockInfo const& _parent) const
 	if (!parentHash)
 		return c_genesisDifficulty;
 	else
-		return timestamp >= _parent.timestamp + 8 ? _parent.difficulty - (_parent.difficulty >> 10) : (_parent.difficulty + (_parent.difficulty >> 10));
+		return timestamp >= _parent.timestamp + (c_protocolVersion == 49 ? 5 : 8) ? _parent.difficulty - (_parent.difficulty >> 10) : (_parent.difficulty + (_parent.difficulty >> 10));
 }
 
 void BlockInfo::verifyParent(BlockInfo const& _parent) const

libethcore/CommonEth.cpp

@@ -32,7 +32,7 @@ namespace dev
 namespace eth
 {
 
-const unsigned c_protocolVersion = 51;
+const unsigned c_protocolVersion = 49;
 const unsigned c_databaseVersion = 5;
 
 static const vector<pair<u256, string>> g_units =

test/jsonrpc.cpp

@@ -29,7 +29,7 @@
 #include <libwebthree/WebThree.h>
 #include <libweb3jsonrpc/WebThreeStubServer.h>
 #include <libweb3jsonrpc/CorsHttpServer.h>
-#include <json/json.h>
+//#include <json/json.h>
 #include <jsonrpccpp/server/connectors/httpserver.h>
 #include <jsonrpccpp/client/connectors/httpclient.h>
 #include <set>