pgsql: Add: > o Prevent parent tables from altering or dropping

Log Message:
-----------
Add:

o Prevent parent tables from altering or dropping constraints
like CHECK that are inherited by child tables

Dropping constraints should only be possible with CASCADE.

Modified Files:
--------------
pgsql/doc:
TODO (r1.1786 -> r1.1787)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.1786&r2=1.1787)
pgsql/doc/src/FAQ:
TODO.html (r1.290 -> r1.291)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.290&r2=1.291)