pgsql: Reverted waiting for further fixes: Make configuration

Log Message:
-----------
Reverted waiting for further fixes:

Make configuration parameters fall back to their default values when they
are removed from the configuration file.

Joachim Wieland

Modified Files:
--------------
    pgsql/src/backend/access/transam:
        xact.c (r1.236 -> r1.237)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/xact.c.diff?r1=1.236&r2=1.237)
    pgsql/src/backend/utils/misc:
        guc-file.l (r1.48 -> r1.49)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc-file.l.diff?r1=1.48&r2=1.49)
        guc.c (r1.381 -> r1.382)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.381&r2=1.382)
    pgsql/src/include/utils:
        guc_tables.h (r1.31 -> r1.32)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/guc_tables.h.diff?r1=1.31&r2=1.32)