#1227 Documentation building error: docbook dtd problem with sgml

[Renier Morales]

Documentation building error: docbook dtd problem with sgml. Happens when you try to make the documetation in the docs/hld directory. It also happens with the subagent's documentation.

Problem is that the new docbook dtds are not compatible with the old definitions used in the documentation sgml. Need to update the sgml.