[PATCH] Add \ns command to psql

Hi,

Here's a new version of a small patch to psql I'm using locally.

It adds a command \ns to psql which is a shortcut to set the
SEARCH_PATH variable.

I'd like to make a case for including this patch as it makes use of
schemas/namespaces much easier. There was resistance to including this
before just because some developers don't use schemas very much. But
we use a lot of them. And I'm sure we're not alone.

Previously I used just \n but there was some resistance to this
because the single letter commands are becoming scarce.

I've also added tab completion making this command much more useful. I
don't think tab completition would be possible if this command was
defined as a variable (which was another suggestion offered at the
time).

Cheers,

Colin