libusb.c: Make GP_LOG_DEBUG component "libusb"
libusb.c: Make GP_LOG_DEBUG component "libusb"

Replace the debugging component "gphoto2-port-usb" with "libusb", as
the latter actually exists, while the former does not.

We only touch the non-existing "gphtoo2-port-usb" and leave the
"mtp matcher" component alone.


git-svn-id: 40dd595c6684d839db675001a64203a1457e7319@12683 67ed7778-7388-44ab-90cf-0a291f65f57c

gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION,gphoto/libgphoto2.OLDMIGRATION