on to 1.0.21-rc5

Signed-off-by: Nathan Hjelm <hjelmn@me.gov>
diff --git a/ChangeLog b/ChangeLog
index 46c440f..eba6901 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,7 @@
 * Linux: Deal with receiving POLLERR before all transfers have completed
 * Solaris: Add solaris backend
 * Windows: Add Visual Studio 2015 support
+* Windows: Add usbdk backend
 * Prevent attempts to recursively handle events
 * Fix race condition in handle_timeout()
 * Allow transferred argument to be optional in bulk APIs