Extend the ELTL parser to support more complex aliases of

automaton operators such as Strong=G(F($0))->G(F($1)) and
G=R(false, $0).

* src/eltlparse/eltlparse.yy, src/eltlparse/eltlscan.ll: Add
support for more complex aliases.
* src/eltltest/acc.cc, src/eltltest/acc.test: Adjust.
* src/ltlast/nfa.cc, src/ltlast/nfa.hh (arity): Now returns an
unsigned value.
* src/tgbatest/eltl2tgba.test: Adjust.
* src/tgbalagos/eltl2tgba_lacim.cc: Fix sanity.

src/tgbatest/eltl2tgba.cc

@@ -95,7 +95,6 @@ main(int argc, char** argv)
     input += spot::ltl::to_string(f, true);
     spot::ltl::destroy(f);
 
-    // std::cerr << input << std::endl;
     f = spot::eltl::parse_string(input, p, env, false);
     formula_index = 2;
   }

src/tgbatest/eltl2tgba.test

@@ -37,6 +37,7 @@ G=(
     0 0 \$0
   )
 F=U(true, \$0)
+Strong=G(F(\$0))->G(F(\$1))
 R=!U(!\$0, !\$1)
 EOF
 
@@ -114,6 +115,16 @@ check_construct input
 check_true 'Fa'
 check_false '!Fa'
 
+cat >input <<EOF
+include input1
+%
+Strong(a,b)
+EOF
+
+check_construct input
+check_true 'G(F(a))->G(F(b))'
+check_false '!(G(F(a))->G(F(b)))'
+
 cat >input <<EOF
 include input1
 %