<security/pam_appl.h> should be <pam/pam_appl.h> on MacOS X

I decided to build 7.3.1 on MacOS 10.2.3 with PAM support.

% ./configure --with-pam --with-openssl
...
configure: error: header file <security/pam_appl.h> is required for PAM

There is, however, a /usr/include/pam/pam_appl.h. So, I did a
search/replace in configure and replaced it.

% make
...
gcc -traditional-cpp -g -O2 -Wall -Wmissing-prototypes
-Wmissing-declarations -I../../../src/include -c -o auth.o auth.c
auth.c:45:31: security/pam_appl.h: No such file or directory
...
make[3]: *** [auth.o] Error 1

So in auth.c, I did the same find/replace:

#ifdef USE_PAM
#include <pam/pam_appl.h>

I added a file to /etc/pam.d for postgresql:

% cat /etc/pam.d/postgresql
auth required pam_nologin.so
auth sufficient pam_securityserver.so
auth sufficient pam_unix.so
auth required pam_deny.so
account required pam_permit.so
password required pam_deny.so
session required pam_uwtmp.so

And then it just worked: my user login for the machine got me into
psql.

- Aaron