math.dtd was dropped from installation in 2009, see
https://issues.apache.org/ooo/show_bug.cgi?id=97200#c3 :
"In agreement with MIB and MT it was diecided that the Math.dtd should
be removed from the installation set as well since it
a) has incorrect content
b) is no longer used nowadays at all"

Change-Id: Id2a727338c224b0beb4b8def197988ab071a7d94