src,zlib: revert concatenated-stream changes

Revert "src: fix windows build error" and "zlib: support
concatenated gzip files". Treating subsequent data as a
concatenated stream breaks npm install.

This reverts commits 93533e98
and 6f6a9795.

Fixes: https://github.com/joyent/node/issues/8962
PR-URL: https://github.com/joyent/node/pull/8985


Reviewed-By: Julien Gilli <julien.gilli@joyent.com>