1Possible upgrades to gzfilebuf:
 2
 3- The ability to do putback (e.g. putbackfail)
 4
 5- The ability to seek (zlib supports this, but could be slow/tricky)
 6
 7- Simultaneous read/write access (does it make sense?)
 8
 9- Support for ios_base::ate open mode
10
11- Locale support?
12
13- Check public interface to see which calls give problems
14  (due to dependence on library internals)
15
16- Override operator<<(ostream&, gzfilebuf*) to allow direct copying
17  of stream buffer to stream ( i.e. os << is.rdbuf(); )