gzip struct not reading past the 1st member

[ddeschenes-1]

The gzip format allows many gzip members concatenated.
The struct file is not supporting that repetition.
It erroneously defines the compressed body until 8 bytes from the end.
This corrupts the body to include bytes that fails the deflate stream.

There is a catch when attempting fix this: the gzip format does not declare length as a prefix nor a suffix.
the compressed payload ends by understanding the inside of the deflate stream.
This is mentioned in issue #396 too.

So, this repeated gzip member issue depends on how the deflate stream can be handled (probably by a 'process').