bug in gunzip 1.2.4

[Andy Jewell]

Subtle, but undeniable.

The bug occurs only when multiple gzip files are concatenated.

If a file (other than the first) starts at a byte offset that is a 
multiple of 32K, gunzip stops, thinking it's done, when in fact it 
isn't.

In gzip.c, at line 677 is the code

   if (!decompress || last_member || inptr == insize) break;
   /* end of file */

The trouble is with the 'inptr == insize'. The problem is, this is 
true if the last file exactly filled the input buffer (it's supposed 
to only be true at EOF, I'm guessing).

I've modified my own code, that generates the gzip file, to vary the 
size of the header so that this case never occurs.

WinZip, MacGZip, Stuffit 6.0 and Solaris gzip 1.3 all work correctly. 
Only straight up 1.2.4 has the problem.

Andy Jewell