Comment out bits that fail with zlib 1.1
Comment out bits that fail with zlib 1.1

Some systems only have zlib 1.1 but the Z_BLOCK, Z_RLE and Z_FIXED
features were obviously added in zlib 1.2. It's ok to just comment them
out since we were not using them anyway. They were only included for
completeness. If anyone does actually want them then shout and I'll
try and cook up a conditional compilcation fix with cpp or something.

tolysz/zlib,tolysz/zlib,tolysz/zlib