Instead of compiling PgPool, why not just install it from package management?
yum install postgresql-pgpool-II
I don't use CentOS, but that's it's package name in Fedora 17, and the two are usually consistent.
Since you're using a PostgreSQL 9.2 installed via Yum on CentOS 5, you're obviously using a 3rd party packaging of PostgreSQL, so you're likely to be using the yum.postgresql.org repository. This repository claims to contain PgPool-II, so try:
yum search pgpool
and see if you find any packages. Get details on them with:
yum info packagename
Otherwise, for compiling PgPool you need the development package for PostgreSQL installed:
yum install postgresql-devel
If that alone doesn't do the trick, try making sure
pg_config is on the
You shouldn't need to specify a
includedir explicitly, as the're in
/usr/lib64) on CentOS and those are default search locations for
gcc. It's most likely that you just don't have the development headers installed.