[plug] type of files

[Jon Miller]

In my /var/spool/up2date directory i noticed a group of files with the .hdr extenstion (see below), any idea what these are:
apache-1.3.14-3.i386.hdr          modutils-2.3.21-1.i386.hdr
apache-manual-1.3.14-3.i386.hdr   mount-2.10m-6.i386.hdr
bind-utils-8.2.2_P7-1.i386.hdr    ncurses-5.2-2.i386.hdr
cpp-2.96-69.i386.hdr              netscape-common-4.76-1.i386.hdr
cyrus-sasl-1.5.24-11.i386.hdr     netscape-communicator-4.76-1.i386.hdr
e2fsprogs-1.18-16.i386.hdr        openssh-2.3.0p1-4.i386.hdr
ed-0.2-19.i386.hdr                openssh-askpass-2.3.0p1-4.i386.hdr
emacs-20.7-17.i386.hdr            openssh-askpass-gnome-2.3.0p1-4.i386.hdr
emacs-X11-20.7-17.i386.hdr        openssh-clients-2.3.0p1-4.i386.hdr
esound-0.2.20-1.i386.hdr          openssh-server-2.3.0p1-4.i386.hdr
fetchmail-5.5.0-3.i386.hdr        pam-0.72-37.i386.hdr
fvwm-1.24r-24.i386.hdr            php-4.0.3pl1-1.i386.hdr
gcc-2.96-69.i386.hdr              pine-4.30-2.i386.hdr
gcc-c  -2.96-69.i386.hdr          python-xmlrpc-1.2.1-1.i386.hdr
ghostscript-5.50-8.i386.hdr       slocate-2.4-1.i386.hdr
git-4.3.20-6.i386.hdr             sysklogd-1.3.33-8.i386.hdr
glibc-2.2-12.i386.hdr             tcsh-6.10-1.i386.hdr
glibc-devel-2.2-12.i386.hdr       tmpwatch-2.6.2-1.7.i386.hdr
glibc-profile-2.2-12.i386.hdr     up2date-2.1.7-1.i386.hdr
gnorpm-0.95.1-5.i386.hdr          up2date-gnome-2.1.7-1.i386.hdr
gnupg-1.0.4-9.i386.hdr            usermode-1.37-2.i386.hdr
iputils-20001010-1.i386.hdr       xanim-2.80.1-12.i386.hdr
libstdc  -2.96-69.i386.hdr        xfishtank-2.1tp-7.i386.hdr
libstdc  -devel-2.96-69.i386.hdr  xinetd-2.1.8.9pre11-1.i386.hdr
mod_perl-1.24-6.i386.hdr