On OpenBSD USB controllers are shown as normal devices, making the
itinial limit too small. On a recent machine this value is almost
always exceeded, so bump it.

Index: libusb/core.c
--- libusb/core.c.orig
+++ libusb/core.c
@@ -612,7 +612,7 @@ libusb_free_device_list(list, 1);
  * which grows when required. it can be freed once discovery has completed,
  * eliminating the need for a list node in the libusb_device structure
  * itself. */
-#define DISCOVERED_DEVICES_SIZE_STEP 8
+#define DISCOVERED_DEVICES_SIZE_STEP 16
 
 static struct discovered_devs *discovered_devs_alloc(void)
 {
