ROME (Reuters) - Air Italy's investors agreed on Tuesday to place the struggling Italian carrier into liquidation, the airline said citing "persistent and structural market problems".The decision was taken "unanimously", the carrier said, but in a separate statement Qatar Airways, which holds a 49% stake, said it would have been ready to support the relaunch and growth of the airline. "Qatar Airways was ready once again to play its part in supporting the growth of the airline, but this would..