Externals: Update libusb to 1.0.23-rc1

Now has support for isochronous transfers in the WinUSB backend,
which may or may not work better than the UsbDk backend.

Externals/libusb/autogen.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+set -e
+
+./bootstrap.sh
+if test -z "$NOCONFIGURE"; then
+    exec ./configure --enable-examples-build --enable-tests-build "$@"
+fi