It are not the glibc kernel headers that are used for the driver to compile but the headers from the linux kernel itself.
On RH 7.x the src is /usr/src/linux-2.4.X. Next to that there's a symlink linux-2.4 (or perhaps they still use a symlink called linux) to linux-2.4.X.
Likely that symlink still points to linux-2.4.18-3 instead of -5. If this is the case then it is logic that you get unresolved symbols since the 2.4.18-3 headers are used.