Like the Little Engine That Could, Microsoft's beleaguered Surface tablet keeps chugging uphill—and refuses to quit.Its latest achievement: In Microsoft's latest quarterly earnings report, its Surface line pulled in $1.1 billion in revenue, a 24% increase over the year-earlier period. The company's flagship tablet, the Pro 3—an expensive but essentially full-fledged Windows machine—led the way.These number suggest that the Surface, a sore point for Microsoft just a few months ago, may have turned the corner.