Log Message:
-----------
When a GUC string variable is not set, print the empty string (in SHOW etc.),
not "unset". An "unset" state doesn't really exist; all variables behave
like an empty string value if the string being pointed to has not been
initialized.
Modified Files:
--------------
pgsql/src/backend/utils/misc:
guc.c (r1.330 -> r1.331)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.330&r2=1.331)