Add zlib-ng

[mathomp4]

Per a note on HDF5, zlib-ng seems to be faster than "old" zlib. Per a note:

I have done some quick serial comparisons between “normal” zlib and zlib-ng and I get anywhere from 50% faster to 80% faster (1/2 to 1/5 the runtime) with zlib-ng. Again, not rigourous in anyway just some quick tests on some medium to very large files.

[mathomp4]

So, I did some tests on discover with a test Baselibs using zlib-ng.

1. Everything I see shows that GEOS is zero-diff using zlib-ng compare to "old" zlib.
2. I do not see any slowdown when using deflation in GEOS, though that is hard to quantify in someways since IOServer "hides" a lot of that due to async
3. It looks like zlib-ng is faster in testing with ncks. I did some test runs with ncks -L where ncks was linked to old or new zlib:

Compression Level	zlib (sec)	zlib-ng (sec)	Speedup
2	39.0	27.2	1.43x
5	59.4	34.6	1.72x
9	247.2	114.4	2.16x