compiling ddd on centos 5

I am running CentOS 5 (which is basically the same as RedHat EL5), with 
xorg-x11 7.1 and gnome.  I have tried to configure ddd-3.3.11, as well 
as 3.3.11-test2 and 3.3.11-test5.  When I run ./configure, it fails (for 
all 3 versions) at this point:

checking for XOpenDisplay in -lX11... no
configure: error: The X11 library '-lX11' could not be found.
                  Please use the configure options '--x-includes=DIR'
                  and '--x-libraries=DIR' to specify the X location.
                  See the files 'config.log' and 'ddd/config.log'
                  for further diagnostics.

I've have openmotif-2.3 installed via an rpm package.  I tried using 
lesstif as well, but it failed to compile, saying "The development 
package of the X Window System is required to compile LessTif, must be 
at least X11r5."  So it doesn't look like I can use lesstif in this 
environment.

So I'm guessing some things have changed in xorg x11 version numbering 
and library locations, and this is causing the problem.  I tried setting 
--x-includes and --x-libraries to a few different things but to no avail.

Any ideas to work around this or what to set x-libraries and x-includes 
to?  Anyone get ddd to compile under CentOS 5 or RedHat Enterprise Linux 
5?  Thanks,

Rob