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/eltltest/acc.test

@@ -22,6 +22,18 @@ A(1,a,a|b)&X(!f)
 EOF
 run 0 ./acc input || exit 1
 
+cat >input <<EOF
+include prelude
+A=(
+    0 1 \$2
+    1 2 \$0
+    accept 0
+  )
+%
+A(1,a)
+EOF
+run 1 ./acc input || exit 1
+
 cat >input <<EOF
 X=(
     0 1 true