www cleanup mega commit:
- Move includes.nav*.sgml to share/sgml/navibar.ent and <lang>/share/sgml/navibar.l10n.ent.
- Move includes.sgml and includes.xsl to share/sgml/common.ent, share/sgml/header.ent, <lang>/share/sgml/l10n.ent, and <lang>/share/sgml/header.l10n.ent.
- Move most of XSLT libraries to share/sgml/*.xsl and <lang>/share/sgml/*.xsl.
- Move news.xml and other *.xml files for the similar purpose to share/sgml/*.xml and <lang>/share/sgml/*.xml.
- Switch to use a custom DTD for HTML document. Now we use "-FreeBSDDTD HTML 4.01 Transitional-Based Extension", which is HTML 4.01 + some entities previously pulled via "<!ENTITY % includes SYSTEM "includes.sgml"> %includes;" line. The location of entity file will be resolved by using catalog file.
- Add DOCTYPE declearation to XML documents. This makes the followings possible:
- Use of &foo; entities for SGML in an XML file instead of defining {$foo} as the same content.
- &symbolic; entities for Latin characters.
- Duplicated information between SGML and XML, or English and translated doc, has been removed as much as possible.