LinuxQuestions.org - how to find and install 32-bit X11 libraries on 64-bit ubuntu 10.04

I just created a new 64-bit ubuntu 10.04 system with codeblocks 10.05 to continue developing a 3D graphics engine/server that I put aside about 1 year ago. After some futzing, I can get simple new test projects to compile and execute, but I cannot get my 3D engine to compile.

The problem is the following. The compiler appears to compile all the files successfully, but then stops and issues the following error message:

ld cannot find -lX11

I only had the 32-bit implementation of my code working when I stopped developing a year ago, so I need to get that working first.

As far as I can tell, the problem is this. I installed the xorg-dev package, which installed the 64-bit include files and library files, but not the 32-bit include files and library files. Try as I might, I cannot find any separate package that includes the 32-bit include files and library files. Actually, I assume a single set of include files will support both 32-bit and 64-bit development... but I'm pretty sure I do need to install a set of 32-bit libraries on my computer to compile this application. I did manage to find and install both 32-bit and 64-bit versions of the OpenGL libraries, but I can't find the X11 files.

Is this probably my problem? If so, how do I download and install those 32-bit libraries on my 64-bit ubuntu 10.04 system?