Yahoo coughed up a lot of cash to land its hotshot new CEO. Marissa Mayer's compensation package could be worth an eye-popping $71 million over the next five years, according to regulatory documents Yahoo filed on Thursday -- and it would top $120 million if an extra batch of stock grants that she is eligible for comes through. Mayer's pay package is by far the most lavish that the company has offered to its recent string of CEOs. On top of a $1 million annual salary and $2 million target bonus…