ltlfilt: implement --reject-word and --accept-word

* bin/common_range.hh: Store the common definition of words.
* bin/autfilt.cc: Use it.
* bin/ltlfilt.cc: Likewise, and implement those two options.
* tests/core/acc_word.test: Test them.
* doc/org/autfilt.org: Augment the last example to point out
that it can now be done with ltlfilt.
* NEWS: Mention the new options.

doc/org/autfilt.org

@@ -756,3 +756,25 @@ Fa U !b
 Fb R F!b
 XF!b U (!b & (!a | G!b))
 #+end_example
+
+Note that the above example could be simplified using the
+=--accept-word= and =--reject-word= options of =ltlfilt= directly.
+However this demonstrates that using =--stats=%M=, it is possible to
+filter formulas based on some properties of automata that have been
+generated by from them.  The translator needs not be =ltl2tgba=: other
+tools can be wrapped with [[file:ltldo.org][=ltldo --name=%f=]] to ensure they work well
+in a pipeline and preserve the formula name in the HOA output.  For
+example Here is a list of 5 LTL formulas that =ltl2dstar= converts to
+Rabin automata that have exactly 4 states:
+
+#+BEGIN_SRC sh :results verbatim :exports both
+randltl -n -1 a b | ltlfilt --simplify --remove-wm |
+  ltldo ltl2dstar --name=%f | autfilt --states=4 --stats=%M -n 5
+#+END_SRC
+
+#+RESULTS:
+: Gb | G!b
+: b R (a | b)
+: (a & !b & (b | (F!a U (!b & F!a)))) | (!a & (b | (!b & (Ga R (b | Ga)))))
+: (a & (a U !b)) | (!a & (!a R b))
+: a | G((a & GFa) | (!a & FG!a))