LONDON (Reuters) - Oil fell on Monday, in line with another decline across global stock markets, which came under pressure from concern about a U.S. government shutdown and a worsening world economy.The price of oil has already fallen by more than 30 percent so far this quarter to its lowest since the third quarter of 2017, as investors have grown increasingly wary of the impact to global growth, and crude demand, from an escalating trade dispute between the United States and China.The U.S...