Build failures on RedHat 3.0 with openssl/kerberos

I try to build 8.1.3 with:

./configure --prefix=/usr/local/pgsql8.1.3 --with-openssl --with-pam
--enable-thread-safety

It fails the openssl test, saying openssl/ssl.h is unavailable. Digging
deeper, I find that it is because the test program with

#include <openssl/ssl.h>

is failing because it can't include krb5.h.

Based on another post, I tried adding "--with-krb5". That explicitly
aborted with it unable to find krb5.h. I then tried:

./configure --prefix=/usr/local/pgsql8.1.3 --with-openssl --with-pam
--enable-thread-safety --with-krb5 --with-includes=/usr/kerberos/include

Now it gets past both the openssl and kerberos, but bites the dust with:

configure: error:
*** Thread test program failed. Your platform is not thread-safe.
*** Check the file 'config.log'for the exact reason.
***
*** You can use the configure option --enable-thread-safety-force
*** to force threads to be enabled. However, you must then run
*** the program in src/tools/thread and add locking function calls
*** to your applications to guarantee thread safety.

If I remove the --with-krb5, it works. Why does enabling Kerberos break
threads?

I haven't been able to find any issues in the archives with krb5 and
threads. Am I missing something here?

Wes