merge ltlvisit/ ltlast/ ltlenv/ into a single tl/ directory

The ltl prefix does not make a lot of sens anymore (since we
support psl as well).  ltlast/ and ltlenv/ were almost empty.
And ltlvisit/ did not contain any visitor anymore.

* src/ltlvisit/, src/ltlast/, src/ltlenv/: Merge into...
* src/tl/: ...this.
* NEWS: Mention the change.
* README, bench/stutter/stutter_invariance_formulas.cc,
bench/stutter/stutter_invariance_randomgraph.cc, configure.ac,
doc/org/tut01.org, doc/org/tut02.org, doc/org/tut10.org, doc/tl/tl.tex,
iface/ltsmin/ltsmin.hh, iface/ltsmin/modelcheck.cc, src/Makefile.am,
src/bin/autfilt.cc, src/bin/common_output.cc, src/bin/common_output.hh,
src/bin/common_r.hh, src/bin/common_trans.cc, src/bin/genltl.cc,
src/bin/ltl2tgba.cc, src/bin/ltl2tgta.cc, src/bin/ltlcross.cc,
src/bin/ltldo.cc, src/bin/ltlfilt.cc, src/bin/ltlgrind.cc,
src/bin/randltl.cc, src/kripke/kripkeexplicit.hh,
src/kripkeparse/public.hh, src/parseaut/public.hh, src/priv/accmap.hh,
src/ta/taexplicit.hh, src/ta/tgtaexplicit.hh, src/tests/equalsf.cc,
src/tests/ikwiad.cc, src/tests/length.cc, src/tests/ltlrel.cc,
src/tests/randtgba.cc, src/tests/readltl.cc, src/tests/reduc.cc,
src/tests/syntimpl.cc, src/tests/taatgba.cc, src/tests/tostring.cc,
src/tests/twagraph.cc, src/twa/acc.hh, src/twa/bdddict.cc,
src/twa/bdddict.hh, src/twa/bddprint.cc, src/twa/taatgba.cc,
src/twa/taatgba.hh, src/twa/twa.hh, src/twa/twagraph.cc,
src/twa/twagraph.hh, src/twa/twasafracomplement.cc,
src/twaalgos/compsusp.cc, src/twaalgos/compsusp.hh,
src/twaalgos/dtgbasat.cc, src/twaalgos/hoa.cc,
src/twaalgos/isweakscc.cc, src/twaalgos/lbtt.cc,
src/twaalgos/ltl2taa.cc, src/twaalgos/ltl2taa.hh,
src/twaalgos/ltl2tgba_fm.cc, src/twaalgos/ltl2tgba_fm.hh,
src/twaalgos/minimize.hh, src/twaalgos/neverclaim.cc,
src/twaalgos/randomgraph.hh, src/twaalgos/relabel.hh,
src/twaalgos/remprop.hh, src/twaalgos/stats.cc, src/twaalgos/stutter.cc,
src/twaalgos/translate.hh, wrap/python/spot_impl.i,
src/ltlparse/ltlparse.yy, src/ltlparse/public.hh: Adjust.

src/tl/Makefile.am

@@ -0,0 +1,67 @@
+## -*- coding: utf-8 -*-
+## Copyright (C) 2015 Laboratoire de Recherche et Développement de
+## l'Epita (LRDE).
+##
+## This file is part of Spot, a model checking library.
+##
+## Spot is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or
+## (at your option) any later version.
+##
+## Spot is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+## or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+## License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+AM_CPPFLAGS = -I$(srcdir)/.. -I.. $(BUDDY_CPPFLAGS)
+AM_CXXFLAGS = $(WARNING_CXXFLAGS)
+
+tldir = $(pkgincludedir)/tl
+
+tl_HEADERS =					\
+  apcollect.hh					\
+  contain.hh					\
+  declenv.hh					\
+  defaultenv.hh					\
+  dot.hh					\
+  environment.hh				\
+  exclusive.hh					\
+  formula.hh					\
+  length.hh					\
+  mutation.hh					\
+  nenoform.hh					\
+  print.hh					\
+  randomltl.hh					\
+  relabel.hh					\
+  remove_x.hh					\
+  simpfg.hh					\
+  simplify.hh					\
+  snf.hh					\
+  unabbrev.hh
+
+noinst_LTLIBRARIES = libtl.la
+libtl_la_SOURCES =				\
+  apcollect.cc					\
+  contain.cc					\
+  declenv.cc					\
+  defaultenv.cc					\
+  dot.cc					\
+  exclusive.cc					\
+  formula.cc					\
+  length.cc					\
+  mark.cc					\
+  mark.hh					\
+  mutation.cc					\
+  nenoform.cc					\
+  print.cc					\
+  randomltl.cc					\
+  relabel.cc					\
+  remove_x.cc					\
+  simpfg.cc					\
+  simplify.cc					\
+  snf.cc					\
+  unabbrev.cc