[DOCS] clarify constraint exclusion vs prepared statements

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/9.2/static/ddl-partitioning.html
Description:

Section 5.9.6 of the documentation discusses caveats re use of constraint
exclusion on partitioned tables. It seems the restriction that the query
constraints must be expressed in terms of constants has been lifted, and now
constraints may be expressed in terms of parameterised values.

I'm wondering if the restriction would still apply, though, in the case that
the query is being prepared in advance, then the constraint value passed in
as a parameter at execution time. It seems to me that constraint exclusion
would not be applied in this case, but would like clarification on this
point.