[IPP] [PWG5100.5] Issue #81: Add "ipp-features-supported" value 'document-object' currently registered in 5100.13

[smith.kennedy at hp.com]

[Issue Unconfirmed]

The 'document-object' keyword for "ipp-features-supported" is still in
5100.13. We have 5100.13 open for revision, so a minor update to 5100.5 to
take this in and remove it from 5100.13 might clean this up a bit.

Link: http://www.pwg.org/issues/81