By Ankur Banerjee and Rae Wee SINGAPORE, Jan 5 (Reuters) - Markets may have shrugged off the audacious U.S. capture of Venezuelan President Nicolas Maduro, but some investors warn that geopolitical risks are perhaps being underestimated after Donald Trump threatened further action in the ​Americas. Investors held their nerve on Monday, with stocks in Asia surging and oil prices down modestly although safe-haven flows lifted gold prices, after ‌President Trump said the U.S. would take control of the oil-p ...