Add support for W (weak until) and M (strong release) operators.

* src/ltlast/binop.cc, src/ltlast/binop.cc: Add support for
these new operators.
* src/ltlparse/ltlparse.yy, src/ltlparse/ltlscan.ll: Parse them.
* src/ltltest/reduccmp.test: Add new tests for W and M.
* src/ltlvisit/basicreduce.cc, src/ltlvisit/contain.cc,
src/ltlvisit/lunabbrev.cc, src/ltlvisit/nenoform.cc,
src/ltlvisit/randomltl.cc, src/ltlvisit/randomltl.hh,
src/ltlvisit/reduce.cc, src/ltlvisite/simpfg.cc,
src/ltlvisit/simpfg.hh, src/ltlvisit/syntimpl.cc,
src/ltlvisit/tostring.cc, src/tgba/formula2bdd.cc,
src/tgbaalgos/eltl2tgba_lacim.cc, src/tgbaalgos/ltl2taa.cc,
src/tgbaalgos/ltl2tgba_fm.cc, src/tgbaalgos/ltl2tgba_lacim.cc:
Add support for W and M.
* src/tgbatest/ltl2neverclaim.test: Test never claim output
using LBTT, this is more thorough.  Also we cannot use -N
any more in the spotlbtt.test.
* src/tgbatests/ltl2tgba.cc: Define M and W for ELTL.
* src/tgbatest/ltl2neverclaim.test: Test W and M, and use
-DS instead of -N, because lbtt-translate does not want
to translate these operators for tools that masquerade as Spin.

src/ltlvisit/simpfg.hh

@@ -1,3 +1,5 @@
+// Copyright (C) 2010 Laboratoire de Recherche et Développement de
+// l'Epita (LRDE).
 // Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
 // département Systèmes Répartis Coopératifs (SRC), Université Pierre
 // et Marie Curie.
@@ -30,6 +32,14 @@ namespace spot
   {
     /// \brief Replace <code>true U f</code> and <code>false R g</code> by
     /// <code>F f</code> and <code>G g</code>.
+    ///
+    /// Perform the following rewriting (from left to right):
+    ///
+    /// - true U a = F a
+    /// - a M true = F a
+    /// - false R a = G a
+    /// - a W false = G a
+    ///
     /// \ingroup ltl_visitor
     class simplify_f_g_visitor : public clone_visitor
     {
@@ -46,6 +56,14 @@ namespace spot
 
     /// \brief Replace <code>true U f</code> and <code>false R g</code> by
     /// <code>F f</code> and <code>G g</code>.
+    ///
+    /// Perform the following rewriting (from left to right):
+    ///
+    /// - true U a = F a
+    /// - a M true = F a
+    /// - false R a = G a
+    /// - a W false = G a
+    ///
     /// \ingroup ltl_rewriting
     formula* simplify_f_g(const formula* f);
   }