Build documentation in make html target

To keep the distchecks for the documentation, the documentation has to
be built in the check target instead of distcheck-hook.

While at it, rename doc/.build to doc/_build. This naming is the
default with sphinx 0.6.2.

doc/Makefile.am

@@ -2,6 +2,19 @@ EXTRA_DIST = \
 	conf.py apiref.rst gettingstarted.rst github_commits.c index.rst \
 	tutorial.rst ext/refcounting.py
 
+SPHINXBUILD = sphinx-build
+SPHINXOPTS = -d _build/doctrees -W
+
+html-local:
+	$(SPHINXBUILD) -b html $(SPHINXOPTS) $(srcdir) _build/html
+
+install-html-local: html
+	mkdir -p $(DESTDIR)$(htmldir)
+	cp -r _build/html $(DESTDIR)$(htmldir)
+
+uninstall-local:
+	rm -rf $(DESTDIR)$(htmldir)
+
 clean-local:
-	rm -rf .build
+	rm -rf _build
 	rm -f ext/refcounting.pyc