Log Message:
-----------
Add comment about why BETWEEN uses operator strings and not opclasses,
with URL pointing to email discussion.
Modified Files:
--------------
pgsql/src/backend/parser:
gram.y (r2.651 -> r2.652)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.651&r2=2.652)