Log Message:
-----------
Document which GUC settings are enums and not strings, along with a short
paragraph about what that means.
Modified Files:
--------------
pgsql/doc/src/sgml:
config.sgml (r1.196 -> r1.197)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.196&r2=1.197)