Incorrect size and checksum reported

[Douglas Concors]

When I run gzip 1.5 with the flag -lv, it blindly reads the last 8
bytes of a file and assumes the values are the checksum and length of
the uncompressed data, however the file may have trailing data after
the compressed stream or may not be a gzip stream at all. I would
recommend parsing the file to find the end of the compressed stream
and reading the checksum/size data from there.
-Doug