genltl: add --pps-arbiter-{strict,standard}

* spot/gen/formulas.cc, spot/gen/formulas.hh, bin/genltl.cc: Implement
this.
* NEWS, bin/man/genltl.x, doc/spot.bib: Add documentation.
* tests/core/genltl.test, tests/core/ltlfilt.test: Add some tests.

tests/core/genltl.test

@@ -129,7 +129,7 @@ EOF
 diff output expected
 
 genltl --kr-n2=1..2 --kr-nlogn=1..2 --kr-n=1..2 --gxf-and=0..3 --fxg-or=0..3 \
-       --format=%F=%L,%f |
+       --pps-arbiter-standard=2..3 --pps-arbiter-strict=2..3 --format=%F=%L,%f |
     ltl2tgba --low --det -F-/2 --stats='%<,%s' > out
 cat >exp<<EOF
 kv-psi=1,15
@@ -146,6 +146,10 @@ fxg-or=0,2
 fxg-or=1,3
 fxg-or=2,4
 fxg-or=3,5
+pps-arbiter-standard=2,15
+pps-arbiter-standard=3,23
+pps-arbiter-strict=2,37
+pps-arbiter-strict=3,82
 EOF
 diff out exp
 

tests/core/ltlfilt.test

@@ -534,3 +534,8 @@ cat >exp <<EOF
 F
 EOF
 diff out exp
+
+f1=`genltl --pps-arbiter-standard=2`
+f2=`genltl --pps-arbiter-strict=2`
+run 1 ltlfilt -f "$f2" --implied-by "$f1"
+run 0 ltlfilt -f "$f1" --implied-by "$f2"