Update NOTICE and LICENSE file.

The original bsdiff and bspatch source files are governed by the
BSD-style license with Colin Percival's copyright. The new files added
by the Chromium OS project are licensed under the BSD-style Chromium OS
license.

This patch reflects this situation adding the "LICENSE" file referenced
from the Chromium OS license header with both licenses while keeping
the "NOTICE" file pointing to it.

Bug: None
Change-Id: Ib12712dd68664879358280618f4cc56164cbe514