dot: fix #393

* spot/twaalgos/dot.cc: Add support for option 'E', and default to
rectangle nodes for large labels.
* bin/common_aoutput.cc, NEWS: Document it.
* tests/core/alternating.test, tests/core/dstar.test,
tests/core/readsave.test, tests/core/sccdot.test,
tests/core/tgbagraph.test, tests/python/_product_weak.ipynb,
tests/python/alternation.ipynb, tests/python/atva16-fig2b.ipynb,
tests/python/automata.ipynb, tests/python/decompose.ipynb,
tests/python/gen.ipynb, tests/python/highlighting.ipynb,
tests/python/ltsmin-dve.ipynb, tests/python/ltsmin-pml.ipynb,
tests/python/parity.ipynb, tests/python/pdegen.py,
tests/python/satmin.ipynb, tests/python/stutter-inv.ipynb: Adjust all
test cases.

NEWS

@@ -36,6 +36,12 @@ New in spot 2.8.7.dev (not yet released)
   - ltlsynt --algo=lar uses the new version of to_parity() mentionned
     below.  The old version is available via --algo=lar.old
 
+  - The dot printer is now automatically using rectangles with rounded
+    corners for automata states if one state label have five or more
+    characters.  This saves space with very long labels.  Use --dot=c,
+    --dot=e, or --dot=E to force the use of Circles, Ellipses, or
+    rEctangles.
+
   Library:
 
   - Historically, Spot only supports LTL with infinite semantics
@@ -110,6 +116,13 @@ New in spot 2.8.7.dev (not yet released)
     dealing with n-ary operators and isolating subsets of operands
     that can be relabeled as a single term.
 
+  - print_dot() default was changed to use circles for automata with
+    fewer than 10 unamed states, ellipses for automata with up to 1000
+    unamed states (or named states with up to 4 characters), and
+    rounded rectangles otherwise.  Rectangles are also used for
+    automata with acceptance bullets on states.  The new "E" option
+    can be used to force rectangles in all situations.
+
   Backward-incompatible changes:
 
   - iar() and iar_maybe() have been moved from