pgsql: Fix Kerberos authentication in wake of virtual-hosts changes ---

Log Message:
-----------
Fix Kerberos authentication in wake of virtual-hosts changes --- need
to call krb5_sname_to_principal() always.  Also, use krb_srvname rather
than the hardwired string 'postgres' as the appl_version string in the
krb5_sendauth/recvauth calls, to avoid breaking compatibility with PG
8.0.  Magnus Hagander

Modified Files:
--------------
    pgsql/src/backend/libpq:
        auth.c (r1.127 -> r1.128)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/auth.c.diff?r1=1.127&r2=1.128)
    pgsql/src/backend/utils/misc:
        postgresql.conf.sample (r1.167 -> r1.168)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.167&r2=1.168)
    pgsql/src/interfaces/libpq:
        fe-auth.c (r1.103 -> r1.104)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-auth.c.diff?r1=1.103&r2=1.104)