[NCLUG] X Includes location?

[Rich Young]

So, I'm trying to install Scribus from source, and I'm getting this error in 
the configure output:

checking for X... configure: error: Can't find X includes. Please check your 
installation and add the correct paths!

The problem is, I'm not sure exactly what or where my "X includes" are.  The 
INSTALL doc details how to feed this info to the configure script once you 
have it, but nothing about exactly what it means.  

Running "locate X | grep includes" returns too many results for me to be 
comfortable guessing.  Anyone?

--Rich
(KRUD 8.0 system)