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)