pgsql: Update constraint_exclusion items: < inheritance, and allow it

Log Message:
-----------
Update constraint_exclusion items:

<   inheritance, and allow it to work for UPDATE and DELETE queries
>   inheritance, allow it to work for UPDATE and DELETE queries, and allow
>   it to be used for all queries with little performance impact
< * Allow constraint_elimination to be automatically performed
<
<   This requires additional code to reduce the performance loss caused by
<   constraint elimination.

Modified Files:
--------------
    pgsql/doc:
        TODO (r1.1637 -> r1.1638)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1637&r2=1.1638)
    pgsql/doc/src/FAQ:
        TODO.html (r1.144 -> r1.145)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.144&r2=1.145)