Let's [e5aa1e624a1c6250|change] the testcases so they pass on Fedora (zlib-ng) too.

In zlib-8.8, it doesn't matter much whether $spdyHeaders compress to 261 or to 260 bytes, but it matters that uncompressing results in the original length.

In zlib-8.16, we see that zlib-ng even compresses more than zlib. So we accept anything less than 57648.

Those changes don't affect the intention of the test-cases.