[OGR-HOWTO] Update OGR HOWTO to document PROCESSING "CLOSE_CONNECTION=DEFER"

[dmorissette]

This relates to DMSG Internal bug -- 3025: optimizations to S57 map rendering by
using OGR's PROCESSING "CLOSE_CONNECTION=DEFER". 

I'm filing a doc bug here to make sure that the doc update doesn't fall in a
crack and that Jeff updates the HOWTO before the release.

Frank W wrote:
> Daniel, 
> 
> I have added details on the connection pooling to the OGR HOWTO and passed
> it on to Jeff for review. 

Assigned to Jeff.

[jmckenna@…]

frank's connection pooling text has been reviewed in the dev version of the
ogr-howto