Move to PV53 along with timestamp being strictly > last time.

libethcore/BlockInfo.cpp

@@ -208,7 +208,7 @@ void BlockInfo::verifyParent(BlockInfo const& _parent) const
 		if (parentHash != _parent.hash)
 			BOOST_THROW_EXCEPTION(InvalidParentHash());
 
-		if (timestamp < _parent.timestamp)
+		if (timestamp <= _parent.timestamp)
 			BOOST_THROW_EXCEPTION(InvalidTimestamp());
 
 		if (number != _parent.number + 1)

libethcore/CommonEth.cpp

@@ -32,7 +32,7 @@ namespace dev
 namespace eth
 {
 
-const unsigned c_protocolVersion = 52;
+const unsigned c_protocolVersion = 53;
 const unsigned c_databaseVersion = 5;
 
 static const vector<pair<u256, string>> g_units =