One analyst thinks this stock is a buy with or without a buyout proposal.Investors have sent shares of International Paper (IP 6.44%) higher in recent weeks on reports that the company has attracted the attention of a buyer. At least one Wall Street analyst sees reason to give the stock a look regardless of the merger and acquisition talk.Shares traded up 6% as of 2:30 p.m. ET on Thursday after the company was upgraded at Jefferies Financial Group (JEF -1.78%).There's more than just a possible merger hereIn ...