gzio

[Yoshinori K. Okuji]

I've added a new module gzio right now. It supports decompression of gzipped 
data. It is much more flexible than the automatic decompression in GRUB 
Legacy, because you can use any kind of file object as an underlying data 
stream. gzio itself makes a file-like object by emulating a filesystem. I bet 
that this is a victory in the design of GRUB 2.

Unlike GRUB Legacy, gzio is not automatic. When you want to use that feature, 
you must use grub_gzfile_open or grub_gzio_open to make a file object. This 
is intentional, and I wouldn't change this.

Once you make a file object, it behaves exactly in the same way as an usual 
file object. In fact, you cannot distinguish them unless you look at the 
internal structure.

For now, only 3 modules (multiboot, cat and cmp) use gzio. Please use it 
whenever appropriate.

I tested it only on PC. I'd like to know if it works with big-endian and 
64-bit systems. If you can, please test it and let me know the result.

Okuji