pgsql-server: Whack some sense into the configuration-file-location

Log Message:
-----------
Whack some sense into the configuration-file-location patch.
Refactor code into something reasonably understandable, cause
use of the feature to not fail in standalone backends or in
EXEC_BACKEND case, fix sloppy guc.c table entries, make the
documentation minimally usable.

Modified Files:
--------------
    pgsql-server/doc/src/sgml:
        runtime.sgml (r1.285 -> r1.286)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/runtime.sgml.diff?r1=1.285&r2=1.286)
    pgsql-server/doc/src/sgml/ref:
        postgres-ref.sgml (r1.43 -> r1.44)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/ref/postgres-ref.sgml.diff?r1=1.43&r2=1.44)
        postmaster.sgml (r1.52 -> r1.53)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/doc/src/sgml/ref/postmaster.sgml.diff?r1=1.52&r2=1.53)
    pgsql-server/src/backend/bootstrap:
        bootstrap.c (r1.193 -> r1.194)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/bootstrap/bootstrap.c.diff?r1=1.193&r2=1.194)
    pgsql-server/src/backend/libpq:
        hba.c (r1.130 -> r1.131)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/libpq/hba.c.diff?r1=1.130&r2=1.131)
    pgsql-server/src/backend/postmaster:
        postmaster.c (r1.429 -> r1.430)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/postmaster/postmaster.c.diff?r1=1.429&r2=1.430)
    pgsql-server/src/backend/tcop:
        postgres.c (r1.433 -> r1.434)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/tcop/postgres.c.diff?r1=1.433&r2=1.434)
    pgsql-server/src/backend/utils/misc:
        guc-file.l (r1.25 -> r1.26)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/guc-file.l.diff?r1=1.25&r2=1.26)
        guc.c (r1.239 -> r1.240)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/guc.c.diff?r1=1.239&r2=1.240)
        postgresql.conf.sample (r1.130 -> r1.131)

(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.130&r2=1.131)
    pgsql-server/src/include/utils:
        guc.h (r1.51 -> r1.52)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/utils/guc.h.diff?r1=1.51&r2=1.52)
        guc_tables.h (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/include/utils/guc_tables.h.diff?r1=1.16&r2=1.17)