assertion failure w/extended query protocol

Rushabh Lathia of the EnterpriseDB development team and I have been
doing some testing of the extended query protocol and have found a
case where it causes an assertion failure. Here's how to reproduce:

1. Apply the attached patch to teach psql how to use the extended
query protocol. Compile, install.

2. Start the modified psql and do this:

\set PROTOCOL extended
PREPARE stmt as select 1;
CREATE TEMPORARY TABLE tmptbl AS EXECUTE stmt;

The result is:

TRAP: FailedAssertion("!(qry->commandType != CMD_UTILITY)", File:
"utility.c", Line: 1516)

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company