Change bsdiff to use divsufsort suffix sort library instead of qsufsort.

Divsufsort is more efficient and addresses the problem of bsdiff hanging
on certain files.

Here are some measurements of the delta diff generator comparing the two
suffix sort alogrithms.

qsufsort:
real	4m40.670s
user	4m19.170s
sys	0m6.400s

divsufsort:
real	3m29.426s
user	3m7.890s
sys	0m6.630s

BUG=chrome-os-partner:3785
TEST=Unit tests, created + applied delta and ensured the system updated
properly, manually ran bsdiff against problematic files to ensure it
completed in a timely manner

Change-Id: Ic5d4215a2de5a1845d88fad5c466f1adf0eaccee
Reviewed-on: http://gerrit.chromium.org/gerrit/1080


Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>