For income investors, Pepsi's (PEP) got the right stuff. PepsiCo, the beverage firm, said Monday that it will buy back $15 billion in shares and boost its dividend 7% to $1.92 a share, good for a 2.9% yield. This is the 38th consecutive annual increase. Pepsi plans to buy some $4.4 billion worth of stock this year. "The board's action reflects continued confidence in the growth of our business and our commitment to providing strong cash returns to