Interface Guidelines: migrate to docs/, use DocBookCSS.

DocBookCSS is a mostly-pure-CSS2 implementation of the DocBook standard.
Unlike DocBookXSL which relies on transforming the XML, it utilizes the
XML-styling features of modern web browsers to display the DocBook.

Its appearance still is a long way from the Haiku Book and Userguide, but
it looks (mostly) the same as the old DocBookXSL so we can stop using that.
Eventually we just need to make DocBookCSS use our styling.

docs/interface_guidelines/docbook-css/opera.css

@@ -0,0 +1,33 @@
+/*
+ * opera.css
+ *
+ * Copyright (c) 2004 David Holroyd, and contributors
+ * See the file 'COPYING' for terms of use
+ *
+ * Part of the Docbook-CSS stylesheet
+ *   http://www.badgers-in-foil.co.uk/projects/docbook-css/
+ *
+ * This file contains CSS specific to the Opera browser.
+ */
+ 
+/*
+ * Discovered -o-link from,
+ * http://groups.google.com/groups?q=opera+styles+xml&start=10&hl=en&lr=&ie=UTF-8&newwindow=1&selm=opr6pgr0tgicz8n2%40news.opera.com&rnum=18
+ */
+ulink {
+	-o-link: attr(url);
+	-o-link-source: current;
+}
+
+/*
+ * Given the above rule, it makes sense to have this here too, though it's
+ * not Opera-specific
+ */
+ulink:focus {
+	outline: 1px dotted invert;
+}
+
+/* this was in the example I found, but it doesn't achive much */
+imagedata {
+	-o-replace: attr(fileref)
+}