[xmlroff] Plan for xmlroff 0.3.7

[Tony G. <Ton...@Su...>]

xmlroff 0.3.6 is almost ready, despite Stefan's efforts to remind me of
essential features.

It is, I think, simple and obvious to continue with fo:external-graphic
improvements for xmlroff 0.3.7.

The tasks for xmlroff 0.3.7 as I see them are:

 - Support 'http:' (and other) protocols in URI specifications

 - Improve handling unresolvable 'src' URI specifications (to be done after
   'http:' support)

 - Handle more fo:external-graphic properties and handle their
   interdependencies:

    - Handle when one of 'content-width' or 'content-height' is specified

    - Handle 'scale' attribute

   It would be good to also handle non-auto ipd and bpd and 'display-align'
   and 'text-align' but that will take more effort.

 - Add a FoImageManager or similar so the same image isn't opened multiple
   times

 - Handle areas that can't be broken

Regards,


Tony.