docbookx schema links outdated
I noticed while building the docs for local use that the docbookx schema links seem to be outdated. The url linked currently is http://docbook.org/docbook/xml/4.5/docbookx.dtd
but it should be http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd
since the former leads to a 404. The file that needs to be edited is docs/tutorial/C/index-in.docbook
.