A subsidiary of Qatar’s sovereign wealth fund is contributing $375 million to Elon Musk’s buyout of Twitter, according to official US documents published on Thursday. Qatar Holding LLC, the main investment subsidiary of the Qatar Investment Authority (QIA), is one of almost 20 companies that have pledged a total of $7.1 billion for the buyout, according to the United States Securities and Exchange Commission. Saudi Arabia’s Prince Alwaleed bin Talal, chairman of the board at the Kingdom Holding Company (KHC), said KHC would be rolling over its approximately $1.9 billion investment in Twitter -…