THIN LEI WIN  YOUNG African farmers Mavis Gofa and Andrew Goodman had a vastly different upbringing - Gofa grew up on a one-hectare (2.5-acre) farm and could not afford to finish high school, while Goodman's family cultivated 275 hectares and educated him in Britain. But they share the same big dream. Both want a better life for the families who run the world's half a billion small farms, many of whom remain steeped in poverty despite producing about 80% of food consumed in Asia and sub-Saharan Africa, according to the United Nations. It is a tough ask as climate change…