DOCBOOK-APPS: Bug: use id as filename,and root.filename appear mutually exclusive

Using the XSL 1.40 stylesheets,
setting
use.id.as.filename "1" and
root.filename "'index'"
resulted in the root node being written as index.<whatever>

With 1.48 the result is that the root node is written using the id.

IMO the root.filename parameter should override the use.id.as.filename
parameter, or if both behaviours are needed, there should be a parameter
to control that.

Rob