BUG #13581: pg_dump omits extension versions

The following bug has been logged on the website:

Bug reference:      13581
Logged by:          Nick Barnes
Email address:      nickbarnes01@gmail.com
PostgreSQL version: 9.4.4
Operating system:   CentOS 6.6
Description:

pg_dump does not include a VERSION clause in CREATE EXTENSION statements. As
a result, the restored database will receive the default extension version
on the target cluster.

This can cause the restore to fail, if for example the structure of the
extension's configuration tables has changed, or the database has
dependencies on a dropped function, type, etc.

I realise that the VERSION clause can't be emitted by default, since old
versions of contrib extensions are not installable. Would an
--include-extension-version=<name> option be feasible?