bin: introduce autcross

Fixes #252.

* NEWS: Mention it.
* bin/autcross.cc, bin/man/autcross.x, doc/org/autcross.org: New
files.
* bin/Makefile.am, bin/man/Makefile.am, doc/org/tools.org,
doc/Makefile.am: Add them.
* bin/autfilt.cc: Use is_universal() instead of is_deterministic().
* bin/common_hoaread.hh, bin/common_trans.cc, bin/common_trans.hh,
bin/ltlcross.cc, bin/ltldo.cc: Factor some bits common between
ltlcross, ltldo and autcross.
* tests/core/autcross.test, tests/core/autcross2.test: New files.
* tests/Makefile.am: Add them.
* tests/core/dra2dba.test, tests/core/sbacc.test,
tests/core/streett.test: Use autcross.

NEWS

@@ -2,6 +2,14 @@ New in spot 2.3.5.dev (not yet released)
 
   Tools:
 
+  - genaut is a new binary that produces families of automata defined
+    in the literature (in the same way as we have genltl for LTL
+    formulas).
+
+  - autcross is a new binary that compares the output of tools
+    transforming automata (in the same way as we have ltlcross for
+    LTL translators).
+
   - autfilt learned to build the union (--sum) or the intersection
     (--sum-and) of two language by putting two automata side-by-side
     and fiddling with the initial states.  This complement the already
@@ -11,9 +19,6 @@ New in spot 2.3.5.dev (not yet released)
   - autfilt learned to complement any alternating automaton with
     option --dualize.
 
-  - genaut is a binary to produce families of automata defined in the
-    literature (in the same way as we have genltl for LTL formulas).
-
   - autfilt learned --split-edges to convert labels that are Boolean
     formulas into labels that are min-terms.  (See spot::split_edges()
     below.)