vim 5.3, gzip files, and Debian Slink

[John Davis <davis@bops.com>]

Hello

I recently discovered that vim allows editing of gzip'd files.  However,
in my case, this capability is only available on my stock debian
installation where I installed the vim package and not on my custom
debian installation where I installed/Make'd vim myself.

I tried to rebuild/config/make vim with gzip options, but I couldn't
find any such option.  (I searched for gzip, and gz in the man page of
vim, the vim Makefile, vim feature.h, and vim configure but never found
it.)  I did notice that vim --version on the two machines were slightly
different.  The most obvious of which was that the stock debian version
included a "-DDEBIAN" switch.  I also looked for that define in the vim
source config files, but I didn't find it either.

Does Debian somehow do something to the gzip files before vim edits them
or something?  Is magic involved?

Many Thanks.