imlib won't recognize new libpng

[Dave Reed <dreed capital edu>]

I'm still running RedHat 4.2 (with all the errata) and want to
experiment with gnome.  I installed the latest glib and gtk
development versions and then tried to install imlib-1.8.1 from the
.tar.gz file.  It complained about an old png library so I downloaded
the new png library and compiled it, installed it in a directory
and added the directory containing the libpng files to /etc/ld.so.conf
(and ran ldconfig), but imlib still doesn't find it during the
.configure

configure: warning: *** Native PNG support will not be built (PNG
library is too old) ***

Because of this gnome-libs won't compile.  How can I make the
.configure script find my new libpng?

Thanks,
Dave
dreed@capital.edu