Thanks for the tests; I'll review and commit them tomorrow morning.

> Even if that means that there is no test which checksums an
> entire superlarge mmap() region.

Bear in mind that the test is only to be removed from 2.7; it will still
be present in the 3.* branches, where crc32() and adler32() actually can
accept such large inputs.

@haypo, @pitrou: Are there any objections to removing test_big_buffer()
from Lib/test/test_zlib.py? If not, I think we can close this issue once
that and the additional mmap tests are committed.