BUG #6685: Concurrency fault in create table

The following bug has been logged on the website:

Bug reference:      6685
Logged by:          Mark Thornton
Email address:      mthornton@optrak.com
PostgreSQL version: 9.1.4
Operating system:   Ubuntu 12.04
Description:=20=20=20=20=20=20=20=20

Executing
create table child_a () inherits (parent)
create table child_b () inherits (parent)

concurrently (two separate connections) results in an error "concurrent
tuple update".

Postgres should be responsible for serializing updates to the shared
resource (whatever it is).