docs: install the generated html files when make install is run

Previously, only the API docs were installed, rather than the
complete documentation set.  This commit ensures the complete
documentation set is installed.

docs/Makefile.am

@@ -26,6 +26,11 @@ devhelphtml =			\
   devhelp/libvirt-libvirt.html	\
   devhelp/libvirt-virterror.html
 
+css =         \
+  generic.css \
+  libvirt.css \
+  main.css
+
 devhelppng =		\
   devhelp/home.png	\
   devhelp/left.png	\
@@ -76,7 +81,7 @@ EXTRA_DIST=					\
   site.xsl newapi.xsl news.xsl page.xsl \
   $(dot_html) $(dot_html_in) $(gif) $(apihtml) $(apipng) \
   $(devhelphtml) $(devhelppng) $(devhelpcss) $(devhelpxsl) \
-  $(xml) $(fig) $(png) \
+  $(xml) $(fig) $(png) $(css) \
   $(patches) \
   sitemap.html.in \
   todo.pl todo.cfg-example
@@ -167,6 +172,8 @@ rebuild: api all
 
 install-data-local:
 	$(mkinstalldirs) $(DESTDIR)$(HTML_DIR)
+	for f in $(css) $(dot_html) $(gif) $(png); do \
+	  $(INSTALL) -m 0644 $(srcdir)/$$f $(DESTDIR)$(HTML_DIR); done
 	-$(INSTALL) -m 0644 $(srcdir)/Libxml2-Logo-90x34.gif $(DESTDIR)$(HTML_DIR)
 	$(mkinstalldirs) $(DESTDIR)$(HTML_DIR)/html
 	for h in $(apihtml); do \