use relative include path

on some systems (Linux distros) the file can reside elsewhere

Author: vladak

user-access.tex

@@ -413,7 +413,7 @@
 \item In Unix, there are many data types such as \verb#uid_t#, \verb#gid_t#,
 \verb#size_t#, \verb#pid_t#, etc.  In general, these are integer types and you
 can often find them in the
-ifdef([[[NOSPELLCHECK]]], [[[\texttt{/usr/inc{}lude/sys/types.h}]]]) header
+ifdef([[[NOSPELLCHECK]]], [[[\texttt{sys/types.h}]]]) header
 file.
 \item Solaris has the \texttt{pcred} command that provides process
 identification information in a simple form: