By Mark Trevelyan LONDON (Reuters) -Russian President Vladimir Putin said on Wednesday he was introducing martial law in four Russian-occupied regions of Ukraine that Moscow claimed last month as its own territory but is struggling to defend from Ukrainian advances. In televised remarks to members of his Security Council, Putin boosted the security powers of all Russia’s regional governors and ordered the creation of a special coordinating council under Prime Minister Mikhail Mishustin to step up the faltering war effort. He said the “entire system of state administration”, not only the specia…