PARIS (Reuters) - Boeing is in talks with other airlines for sales of its grounded 737 MAX after receiving a letter of intent for 200 planes from British Airways owner IAG at the Paris Airshow, its sales chief said on Thursday.Senior vice president Ihssane Mounir also dismissed the launch of a longer-range single-aisle jet by rival Airbus as suitable for only a "sliver" of the market that Boeing hopes to address with a possible all-new mid-market plane.He declined to comment on the timing of..