BUG #5729: psql stopped after invalid surrogate pair

The following bug has been logged online:

Bug reference: 5729
Logged by: Alan Choi
Email address: alan.choi@emc.com
PostgreSQL version: Version 9.0.1-1
Operating system: Mac OS X 10.6.4
Description: psql stopped after invalid surrogate pair
Details:

psql stopped and quit if it encountered an invalid surrogate pair.

Execute the psql client.

Server [localhost]:
Database [postgres]:
Port [5432]:
Username [postgres]:
Password for user postgres:
psql (9.0.1)
Type "help" for help.

postgres=# select E'\uD834';
invalid YY_START

Press <return> to continue...
logout

[Process completed]

The E'\uD834' is an invalid surrogate pair but psql should report it as a
regular parsing error.