pgsql-server: Allow configuration files to be placed outside the data

Log Message:
-----------
Allow configuration files to be placed outside the data directory.

Add new postgresql.conf variables to point to data, pg_hba.conf, and
pg_ident.conf files.

Needs more documentation.

Modified Files:
--------------
    pgsql-server/doc/src/sgml:
        runtime.sgml (r1.268 -> r1.269)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/runtime.sgml.diff?r1=1.268&r2=1.269)
    pgsql-server/doc/src/sgml/ref:
        postmaster.sgml (r1.50 -> r1.51)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/ref/postmaster.sgml.diff?r1=1.50&r2=1.51)
    pgsql-server/src/backend/bootstrap:
        bootstrap.c (r1.185 -> r1.186)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/bootstrap/bootstrap.c.diff?r1=1.185&r2=1.186)
    pgsql-server/src/backend/libpq:
        hba.c (r1.125 -> r1.126)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/libpq/hba.c.diff?r1=1.125&r2=1.126)
    pgsql-server/src/backend/postmaster:
        postmaster.c (r1.406 -> r1.407)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/postmaster.c.diff?r1=1.406&r2=1.407)
    pgsql-server/src/backend/tcop:
        postgres.c (r1.422 -> r1.423)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/tcop/postgres.c.diff?r1=1.422&r2=1.423)
    pgsql-server/src/backend/utils/misc:
        guc-file.l (r1.22 -> r1.23)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/guc-file.l.diff?r1=1.22&r2=1.23)
        guc.c (r1.213 -> r1.214)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/guc.c.diff?r1=1.213&r2=1.214)
        postgresql.conf.sample (r1.113 -> r1.114)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.113&r2=1.114)
    pgsql-server/src/include/utils:
        guc.h (r1.48 -> r1.49)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/utils/guc.h.diff?r1=1.48&r2=1.49)