Upgrade to zlib >=0.6.

Fix: 7.4.2 compat.

PVP compliance: upper version bound.

Revert noise and relax zlib min version back to 0.5.3 (part 1/2).

Revert noise and relax zlib min version back to 0.5.3 (part 2/2).

Test cases for maybeDecompress.

Use edsko's implementation of maybeDecompress; add test case.

Fixup.

maybeDecompress: test suite work-around.

Cleanup.

Relax zlib upper bound.

maybeDecompress: add mysteriously failing test cases.

7.4 compat for test cases.