show how to implement product in Python

* wrap/python/tests/product.ipynb: New file.
* wrap/python/tests/Makefile.am, doc/org/tut.org: Add it.
* wrap/python/tests/ipnbdoctest.py: Ignore %timeit results.
* wrap/python/spot_impl.i: Add bindings for
set_state_names()/get_state_names().
* spot/twaalgos/product.cc: Fix computation of properties.
* doc/org/hoa.org: Name.
* NEWS: Update.

doc/org/hoa.org

@@ -584,6 +584,9 @@ labels whenever that is possible.  The option is named =k= (i.e., use
 is used to describe a Kripke structure.
 
 ** Property bits
+   :PROPERTIES:
+   :CUSTOM_ID: property-bits
+   :END:
 
 The =HOA= format supports a number of optional =property:= tokens.
 These properties can be useful to speedup certain algorithms: for

doc/org/tut.org

@@ -52,6 +52,8 @@ real notebooks instead.
 - [[https://spot.lrde.epita.fr/ipynb/accparse.html][accparse.ipynb]] exercises the acceptance condition parser
 - [[https://spot.lrde.epita.fr/ipynb/acc_cond.html][acc_cond.ipynb]] documents the interface for manipulating acceptance
   conditions
+- [[https://spot.lrde.epita.fr/ipynb/product.html][product.ipynb]] shows how to re-implement the product of two automata
+  in Python
 - [[https://spot.lrde.epita.fr/ipynb/randltl.html][randltl.ipynb]] demonstrates a Python-version of [[file:randltl.org][=randltl=]]
 - [[https://spot.lrde.epita.fr/ipynb/decompose.html][decompose.ipynb]] illustrates the =decompose_strength()= function
 - [[https://spot.lrde.epita.fr/ipynb/testingaut.html][testingaut.ipynb]] shows the step necessary to build a testing