libusb: upgraded package to upstream

Upgraded dev-libs/libusb to version 1.0.21 on amd64

Updating libusb from 1.0.20 to 1.0.21 (amd64), even though
similar problem can still be found (gcc build works but
not llvm build).

BUG=chromium:723145
TEST=sudo emerge libusb

Change-Id: I80187b39f3ab5dbaecce87588b1c0a6c8a193a83
Reviewed-on: https://chromium-review.googlesource.com/513502
Commit-Ready: YH Lin <yueherngl@chromium.org>
Tested-by: YH Lin <yueherngl@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
5 files changed