PAM: Include header file security/pam_appl.h
    
    We need this file for declaration of pam functions
        pam_get_item, pam_putenv, pam_set_data, pam_strerror, pam_set_item
    
    There is already test in configure script for this header file,
    but it was not included in pam_sss.c
    
    sh-4.2$ git grep pam_appl.h
    src/external/pam.m4:AC_CHECK_HEADERS([security/pam_appl.h ...
    src/providers/data_provider_be.c:#include <security/pam_appl.h>
    src/providers/proxy/proxy.h:#include <security/pam_appl.h>
    src/providers/proxy/proxy_child.c:#include <security/pam_appl.h>
    src/responder/pam/pamsrv.h:#include <security/pam_appl.h>
    src/sss_client/pam_test_client.c:#include <security/pam_appl.h>
    src/util/auth_utils.h:#include <security/pam_appl.h>
    
    Reviewed-by: Sumit Bose <sbose@redhat.com>
    (cherry picked from commit 81d6673764c4e2f635482be1efd52eba3ab5a27f)