LONDON - In the latest in a series of gestures toward modernization that would once have seemed improbable, Saudi Arabia announced on Monday that it would allow commercial movie theaters to open for the first time in more than 35 years.The moves to allow access by early 2018, part of a broad campaign by the crown prince, Mohammed bin Salman, to transform Saudi society, followed measures like giving women the right to drive and to attend soccer games, and allowing concerts and other forms of public entertainment.At the same time, the crown prince has embarked on a broad drive against corruption, holding members of the Saudi elite in a luxury hotel, in what has been described as an effort to force them to repay billions of dollars diverted into personal coffers from other transactions. Critics say the detentions were intended to neutralize potential challengers.The announcement on Monday is in keeping with a promise by the 32-year-old crown prince to return Saudi Arabia to a more...