password change / table creation

There are two questions in the pgsql-admin mailing list which are very often
asked, but nobody seems to have a reasonable answer to these.
So I decided to post them here and I hope anyone can help me (and many
others) !

- Can a PostgreSQL user change his own password without having
"usesuper" set to 't' in pg_shadow ?

I think this should be possible with a PostgreSQL C function (or
PL/Tcl) which alters the "passwd" attribute of the pg_shadow table and
after that copies the contents of this table to the pg_pwd ASCII file
(and generates an empty pg_pwd.reload).
But I have no idea how to manipulate and copy tables within PostgreSQL
C functions.

Does anybody know if there is already such a function or any other way
to achieve the above mentioned functionality ?

- Can the Postgres superuser prevent a user from creating tables in any
database the user likes to ?

It would be good to have a way to restrict the use of the "CREATE
TABLE" SQL statement so that a user can only create tables in
databases he is explicitly allowed to.

Does anyone have an idea how to solve this problem ?

If these two features are not yet implemented I would suggest to think about
implementing them, because I (and many other people) would consider them
as important, especially in practical use.

Please let me know !

Thank you very much
RP. Dumont