Move documentation generating to Valadoc

Generating Vala documentation with GTK-Doc is a bit of PITA. Using
Valadoc is much easier, so we are moving there.

docs/valadoc/gtk-doc/Makefile.am

@@ -0,0 +1,28 @@
+include $(top_srcdir)/vala-globals.mk
+CLEANFILES =
+
+sources = $(top_srcdir)/src/*.vala
+
+gtkdocdir = $(datadir)/gtk-doc/html/matrix-glib
+gtkdoc_DATA = \
+	gtk-doc/matrix-glib/*.txt \
+	gtk-doc/matrix-glib/*.xml \
+	gtk-doc/matrix-glib/xml/*.xml \
+	gtk-doc/matrix-glib/xml/*.top \
+	gtk-doc/matrix-glib/xml/*.bottom \
+	gtk-doc/matrix-glib/*.types \
+	gtk-doc/matrix-glib/sgml.stamp \
+	$(NULL)
+
+$(gtkdoc_DATA): matrix-glib-gtk-doc
+
+matrix-glib-gtk-doc:
+	$(VALADOC) -o gtk-doc/matrix-glib --doclet=gtkdoc \
+	    -X $(top_builddir)/src/matrix-glib.h \
+	    $(VALADOC_FLAGS) $(sources)
+
+all: matrix-glib-gtk-doc
+
+clean-local:
+	rm -rf gtk-doc
+	rm -rf matrix-glib