doc: Improve comments related to device discovery and hotplug

Closes #1013

libusb/core.c

diff --git a/libusb/core.c b/libusb/core.c
index 90eb6d7..3d2f2b4 100644
--- a/libusb/core.c
+++ b/libusb/core.c
@@ -580,7 +580,9 @@
  *
  * The libusb_get_device_list() function can be used to obtain a list of
  * devices currently connected to the system. This is known as device
- * discovery.
+ * discovery. Devices can also be discovered with the hotplug mechanism,
+ * whereby a callback function registered with libusb_hotplug_register_callback()
+ * will be called when a device of interest is connected or disconnected.
  *
  * Just because you have a reference to a device does not mean it is
  * necessarily usable. The device may have been unplugged, you may not have
@@ -611,7 +613,7 @@
  *
  * With the above information in mind, the process of opening a device can
  * be viewed as follows:
- * -# Discover devices using libusb_get_device_list().
+ * -# Discover devices using libusb_get_device_list() or libusb_hotplug_register_callback().
  * -# Choose the device that you want to operate, and call libusb_open().
  * -# Unref all devices in the discovered device list.
  * -# Free the discovered device list.

libusb/hotplug.c

diff --git a/libusb/hotplug.c b/libusb/hotplug.c
index 4bb2d4e..402e693 100644
--- a/libusb/hotplug.c
+++ b/libusb/hotplug.c
@@ -62,7 +62,7 @@
  * A hotplug event can listen for either or both of these events.
  *
  * Note: If you receive notification that a device has left and you have any
- * a libusb_device_handles for the device it is up to you to call libusb_close()
+ * libusb_device_handles for the device it is up to you to call libusb_close()
  * on each device handle to free up any remaining resources associated with the device.
  * Once a device has left any libusb_device_handle associated with the device
  * are invalid and will remain so even if the device comes back.

libusb/libusb.h

diff --git a/libusb/libusb.h b/libusb/libusb.h
index 0b3d854..2825b41 100644
--- a/libusb/libusb.h
+++ b/libusb/libusb.h
@@ -992,7 +992,7 @@
 /** \ingroup libusb_dev
  * Structure representing a USB device detected on the system. This is an
  * opaque type for which you are only ever provided with a pointer, usually
- * originating from libusb_get_device_list().
+ * originating from libusb_get_device_list() or libusb_hotplug_register_callback().
  *
  * Certain operations can be performed on a device, but in order to do any
  * I/O you will have to first obtain a device handle using libusb_open().

libusb/version_nano.h

diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index a0cf63c..7bbbe39 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11661
+#define LIBUSB_NANO 11662