The convention of passing 0 to inflateInit2() to autodetect the window
size is not supported in really old versions of zlib. The only
downside with simply passing in the maximum value (15) is potential
additional memory buffer allocations, but it is a drop in the bucket
for NASM.
Fixes: https://github.com/netwide-assembler/nasm/issues/165
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>