Make sure notation section is included in most intros.

Split introduction sections into separate files to allow the legal notice
 and notation sections appear in all documents without having the history
 show up everplace too.
Add full list of reserved and non-reserved key words in syntax.sgml.
Add a separate chapter to the admin guide on security.

Fix Id tag in chapter headings to allow meaningful file names in html.

 from datatype.sgml into separate files.
Add type conversion information.
Format historical release notes.