doc: make clean should not need latexmk

Report from Joachim Klein.

* doc/tl/Makefile.am (mostlyclean-local): Rename as...
(maintainer-clean-local): ... this.

doc/tl/Makefile.am

-## Copyright (C) 2011, 2012, 2013 Laboratoire de Recherche et
+## -*- coding: utf-8 -*-
+## Copyright (C) 2011, 2012, 2013, 2015 Laboratoire de Recherche et
 ## Développement de l'Epita (LRDE).
 ##
 ## This file is part of Spot, a model checking library.
@@ -44,6 +45,6 @@ $(srcdir)/tl.pdf: $(srcdir)/tl.tex $(srcdir)/tl.bib
 pvc:
 	$(LATEXMK) -pvc $(srcdir)/tl.tex
 
-.PHONY: mostlyclean-local pvc
-mostlyclean-local:
+.PHONY: mainainer-clean-local pvc
+mainainer-clean-local:
 	$(LATEXMK) -c $(srcdir)/tl.tex