Zlib memory leak and leastsize assertion

[etcimon]

This fixes an issue where zlib is not guaranteed to call deflateEnd or inflateEnd.

It also fixes an assertion failure that occurs when the underlying stream is closed prematurely.

[etcimon]

Bump

[s-ludwig]

Sorry for having forgot about this. I meant to comment on this for a while.

[s-ludwig]

I still need to understand the issue with that assertion. This should really have a unit test, but I think that it would be a little safer to, instead of removing the assertion, to set the m_finished flag when a premature end of input is detected.

[etcimon]

The issue is when the connection closes (for an unlimited amount of non-program-related reasons), readChunk -> m_in.leastSize returns 0 and zlib stream sees a premature end of input, and fails on this assertion, so it stands out from other streams where you can end up with a closed connection and fail an enforcement at a higher level to e.g. try again, rather than having the task end unexpectedly as a whole.

[s-ludwig]

I've fixed this locally by adding a check for empty input in readChunk. I'll pull and then commit my changes on top.