doc: correction of LIBUSB_OPTION_WEAK_AUTHORITY availability

Even though its implementation is in linux/usbfs,
in fact it is under `ifdef` and only used by Android builds.

Closes #916

Signed-off-by: Nathan Hjelm <hjelmn@google.com>
diff --git a/libusb/libusb.h b/libusb/libusb.h
index d2dfa20..57ca58f 100644
--- a/libusb/libusb.h
+++ b/libusb/libusb.h
@@ -2102,10 +2102,10 @@
 	 * scan devices in libusb_init.
 	 *
 	 * This option should be set before calling libusb_init(), otherwise
-	 * libusb_init will failed. Normally libusb_wrap_sys_device need set
-	 * this option.
+	 * libusb_init will failed. Normally libusb_wrap_sys_device on Android
+	 * need set this option.
 	 *
-	 * Only valid on Linux-based operating system, such as Android.
+	 * Only valid for Android builds.
 	 */
 	LIBUSB_OPTION_WEAK_AUTHORITY = 2
 };
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 9db83c0..d44ba57 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11618
+#define LIBUSB_NANO 11619