[xml/sgml] w3c-sgml-lib vs w3-dtd-mathml

[Mathieu Malaterre]

I am getting confused with the packaging of w3c-sgml-lib. Should it
replaces w3-dtd-mathml ?
It looks like it should replace at least a portion of it right ? I can
get #355440 to work by only installing w3c-sgml-lib.

However using w3c-sgml-lib (and removing w3-dtd-mathml) I cannot get
#283173 to work.

Questions:
- Should I fill a removal for w3-dtd-mathml ?
- Should I reassign bug #283173 to w3c-sgml-lib ?

Thanks