Remove DTD URL from SGML file (fixes underlying bug of #31)
Remove DTD URL from SGML file (fixes underlying bug of #31)

Some versions of the docbook tools don't support DTD URLs, and in any
case it's undesirable to fetch the DTD over the network when it's
probably on the local machine, so now we don't.

FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs