pgsql: Add support for GSSAPI authentication.

Log Message:
-----------
Add support for GSSAPI authentication.

Documentation still being written, will be committed later.

Henry B. Hotz and Magnus Hagander

Modified Files:
--------------
    pgsql:
        configure (r1.549 -> r1.550)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.diff?r1=1.549&r2=1.550)
        configure.in (r1.516 -> r1.517)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.in.diff?r1=1.516&r2=1.517)
    pgsql/src/backend/libpq:
        auth.c (r1.148 -> r1.149)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/auth.c.diff?r1=1.148&r2=1.149)
        hba.c (r1.160 -> r1.161)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/hba.c.diff?r1=1.160&r2=1.161)
        pg_hba.conf.sample (r1.62 -> r1.63)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/pg_hba.conf.sample.diff?r1=1.62&r2=1.63)
        pqcomm.c (r1.192 -> r1.193)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/pqcomm.c.diff?r1=1.192&r2=1.193)
    pgsql/src/backend/postmaster:
        postmaster.c (r1.530 -> r1.531)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.530&r2=1.531)
    pgsql/src/backend/utils/misc:
        guc.c (r1.404 -> r1.405)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.404&r2=1.405)
        postgresql.conf.sample (r1.218 -> r1.219)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.218&r2=1.219)
    pgsql/src/include:
        pg_config.h.in (r1.117 -> r1.118)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pg_config.h.in.diff?r1=1.117&r2=1.118)
    pgsql/src/include/libpq:
        hba.h (r1.45 -> r1.46)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/libpq/hba.h.diff?r1=1.45&r2=1.46)
        libpq-be.h (r1.58 -> r1.59)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/libpq/libpq-be.h.diff?r1=1.58&r2=1.59)
        pqcomm.h (r1.104 -> r1.105)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/libpq/pqcomm.h.diff?r1=1.104&r2=1.105)
    pgsql/src/interfaces/libpq:
        Makefile (r1.154 -> r1.155)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/Makefile.diff?r1=1.154&r2=1.155)
        fe-auth.c (r1.123 -> r1.124)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-auth.c.diff?r1=1.123&r2=1.124)
        fe-connect.c (r1.347 -> r1.348)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-connect.c.diff?r1=1.347&r2=1.348)
        libpq-int.h (r1.121 -> r1.122)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-int.h.diff?r1=1.121&r2=1.122)