parseaut: preliminary support for reading alternating automata

Currently this only reads universal branches.  The parser (and the
automaton code) do not support universal initial states.

* spot/parseaut/parseaut.yy: Read universal branches.  Deal with
the no-univ-branch/!univ-branch change in HOA 1.1.
* tests/python/alternating.py: Read the output of print_hoa.
* tests/core/parseaut.test: Adjust test output, and add more tests.

tests/python/alternating.py

@@ -69,3 +69,8 @@ State: 1
 State: 2
 [0 | 1] 2
 --END--"""
+
+aut2 = spot.automaton(h)
+h2 = aut2.to_str('hoa')
+print(h2)
+assert h == h2