HONG KONG, Aug 18 (Reuters Breakingviews) – What's the point of a rainy-day fund if you can't use it? South Korea's Samsung Electronics (005930.KS) more than halved its stake in Dutch semiconductor-equipment maker ASML (ASML.AS) to raise an estimated $2 billion for its expansion plans, the Korean Economic Daily reported on Tuesday. Yet the company already has $66 billion in the bank. Trouble is, much of that is probably trapped abroad. Samsung's 11-year-old investment in ASML has been hugely lucrative. In 2012, the Veldhoven-headquartered company tapped its three major customers – the South Korean conglomerate, Taiwan's TSMC (2330.TW) and Intel…