For detailed information about the changes below, please see the git log or
visit: http://log.libusb.info
+2016-07-20: v1.0.21:
+* Darwin: Ignore root hub simulation devices
+* Darwin: Improved support for OS X El Capitan
+* Windows: Add Visual Studio 2015 support
+* Prevent attempts to recursively hande events
+* Fix race condition in handle_timeout()
+* Allow transferred argument to be optional in bulk APIs
+* Various other bug fixes and improvements
+
2015-09-13: v1.0.20
* Add Haiku support
* Fix multiple memory and resource leaks (#16, #52, #76, #81)