MOSCOW - Powerful Russian Prime Minister Vladimir Putin is to give the keynote address to his party's congress on Thursday amid intense speculation he is planning a presidential comeback. Putin is due to speak to the United Russia party that he leads from 9 a.m. GMT in a speech that will be closely watched for hints of his future intentions and comments on the current financial crisis. A day earlier Russia's lower house of parliament gave to overwhelming approval to the second reading of a bill extending the presidential term from four years to six.The Russian...