Bug#1001181: docbook-mathml should switch from w3-dtd-mathml to w3c-sgml-lib

[Adrian Bunk]

Package: docbook-mathml
Version: 1.1CR1-2.1
Severity: serious
Tags: bookworm sid
Control: block 994795 by -1

w3-dtd-mathml contains an older version of mathml2.dtd that no longer
works with libxml2 2.9.12, see #994795 for background.