Merge branch 'jn/maint-doc-user-manual-html-doctype'

* jn/maint-doc-user-manual-html-doctype:
  docs: fix Makefile dependency for user manual
  Documentation: set a !DOCTYPE for user manual

Documentation/Makefile

@@ -279,7 +279,7 @@ $(patsubst %,%.html,$(API_DOCS) technical/api-index): %.html : %.txt
 XSLT = docbook.xsl
 XSLTOPTS = --xinclude --stringparam html.stylesheet docbook-xsl.css
 
-user-manual.html: user-manual.xml
+user-manual.html: user-manual.xml $(XSLT)
 	$(QUIET_XSLTPROC)$(RM) $@+ $@ && \
 	xsltproc $(XSLTOPTS) -o $@+ $(XSLT) $< && \
 	mv $@+ $@

Documentation/docbook.xsl

@@ -1,5 +1,8 @@
 <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
 		version='1.0'>
  <xsl:import href="http://docbook.sourceforge.net/release/xsl/current/html/docbook.xsl"/>
- <xsl:output method="html" encoding="UTF-8" indent="no" />
+ <xsl:output method="html"
+     encoding="UTF-8" indent="no"
+     doctype-public="-//W3C//DTD HTML 4.01//EN"
+     doctype-system="http://www.w3.org/TR/html4/strict.dtd" />
 </xsl:stylesheet>