American Tower agreed to buy Eaton Towers for about $1.85-billion including debt as one of the few international providers of telecommunications infrastructure expands in the fast-growing African market. Both companies have sites in countries such as Ghana and Kenya, and the deal will enable American Tower to build more on the continent, the Boston-based company said in a statement on Thursday. The tie-up will generate about $260-million in property revenue in the first year of ownership, it said.