More than 10,000 developers behind some of the hottest apps on the iPhone (s AAPL), iPod Touch and Android (s GOOG)OS-based smartphones are using Foursquare’s application programming interface to tap into its location and places database, the company says. Foursquare launched its API in November 2009. In a post published Friday on the Foursquare engineering blog, platform evangelist Akshay Patil w