zlib: allow feeding more than 4GB in one go

zlib: allow feeding more than 4GB in one go

Update zlib_post_call() that adjusts the wrapper's notion of avail_in and
avail_out to what came back from zlib, so that the callers can feed
buffers larger than than 4GB to the API.

When underlying inflate/deflate stopped processing because we fed a buffer
larger than 4GB limit, detect that case, update the state variables, and
let the zlib function work another round.

Signed-off-by: Junio C Hamano <gitster@pobox.com>