Ok, not really any fundamental changes, mostly a source reorganization,
but some new features as well:

1. Split off FS specific code for all FS types into subdirectories.
   imagezip.c was just getting unwieldy.  You can now (in theory, I
   haven't enabled this in any easy way) build a version of imagezip
   with only the FSes you care about.

2. As part of the above, localize the filesystem specific headers in
   the subdirs instead of relying on the installed system headers.
   This allows easy building of, for example, BSD FS support under
   Linux.

3. Hacked up the GNUmakefiles some so that imagezip with all FS support
   will build (in the Emulab context) under Linux and FreeBSD 5.1 as
   well as FreeBSD 4.x.  Still a hack, for Linux you need to first do:
	setenv LINUX 1
	setenv HAVE_GCC3 1
	setenv HAVE_LOCALE 1
   and for FreeBSD 5.x:
	setenv HAVE_GCC3 1
	setenv HAVE_LOCALE 1
   these trigger ifdefs in some of the Makefiles to DTRT.  Imagezip
   and frisbee still need a standalone configure...

4. Added support for UFS2 (aka FreeBSD 5.x default filesystems).

5. Added "-S dos-type" option to imagezip.  This is the general form
   of the -b, -l, and -n options to force imagezip to treat the device
   as though it contains a filesystem of the indicated type.