[xliff-tools] PO Repr. Guide: restype attribute for PO Header

[Asgeir Frimannsson]

Hi,

When handling the PO header as a normal translation unit, I would suggest 
setting the 'restype' attribute to 'x-gettext-domain-header'. Any objections 
or comments?

Pros:
 - Enables tools to create custom editor for PO header information.
 - Can be used by TM to ignore translation unit (though, the TM should ignore 
it anyway since it has empty source element)

Cons:
 - Yet another feature to build into filters.

cheers,
asgeir