>4GiB source delta assertion failure

[Ilari Liusvaara <ilari.liusvaara@elisanet.fi>]

Yes, I know trying to delta-compress with 4GiB files is insane, but OTOH,
assertion failures are bugs by defintion.

Delta source: <4GiB of zeroes> <random 64KiB block>
Delta destination: <the same 64KiB block>

This was created using:
$ dd if=/dev/urandom of=test-delta-target bs=64k count=1
$ dd if=test-delta-target of=test-delta-source bs=64k seek=64k

Now running

$ ./test-delta -d test-delta-source test-delta-target test-delta-delta

Crashes with (v1.7.2):

test-delta: diff-delta.c:285: create_delta_index: Assertion `packed_entry - (struct index_entry *)mem == entries' failed.
Aborted


As note: The delta compression format does not allow delta compression to 
properly work in this case (since source offset would need to be 2^32 and
biggest possible offset is 2^32-1), and thus the size of output should be on
order of 66kB.

-Ilari