Procedural language permissions and consequences

For the next release, I'd like to implement permissions for procedural
languages. It would be one permission called USAGE, which allows the user
to create a function using that language. I will reuse the aclitem[]
approach, in the same way as I'm already doing for functions.

The first consequence is that we could get rid of createlang as the
primary means of access control to languages. I would like to install all
languages by default (excluding only those that haven't been included by
"configure"). Would people be afraid if we made the trusted languages
available to all users by default? That would really be a lot more
convenient.

The "trusted" flag could be done away with. However, the current
untrusted languages (pltclu and plperlu) actually use the trusted flag
both as an external access control and internally to decide how to behave.
We could keep the latter use for now, until perhaps someone invents a
generic language configuration mechanism.

Furthermore, we can conveniently eliminate the problems related to finding
all the language handlers as shared libraries. Since all languages are
installed by default we can just link the handlers right into the
postmaster, for which we don't need shared libraries. That should give a
great boost to languages that are currently hard to build, i.e., PL/Perl
and PL/Python. And the build system would become a lot simpler and more
portable.

Any comments on these points?

--
Peter Eisentraut peter_e(at)gmx(dot)net