mod_storage_s3: Enable connection pooling added in latest trunk Speed boost, something like a 30% improvement with http://localhost Small risk of failed requests due to limits on number of requests per connection or timeouts.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```