add pollfds created by libusb before the pollfds add/remove handlers are registered
add pollfds created by libusb before the pollfds add/remove handlers are registered

Ignore-this: b109603c37f56ccdff2ea275b43de82e

Thanks to Nicolas Dandrimont for the patch

darcs-hash:20110519163209-c41ad-dd065e2dac213cf793b1cf9a3ee193bea88177cc

diml/ocaml-usb,diml/ocaml-usb