genltl: typos and shorter descriptions

* bin/genltl.cc: Shorten the descriptions of
the three new LTL families.
* NEWS: Mention those.

NEWS

@@ -12,6 +12,11 @@ New in spot 2.3.0.dev (not yet released)
   - The option (y) has been added to --dot. It splits the universal
     edges with the same targets but different colors.
 
+  - genltl learnt three new families for formulas: --kr-n2=RANGE,
+    --kr-nlogn=RANGE, and --kr-n=RANGE.  These formulas, from
+    Kupferman & Rosenberg [MoChArt'10] are recognizable by
+    deterministic Büchi automata with at least 2^2^n states.
+
   Library:
 
   - spot::twa_run::as_twa() has an option to preserve state names.

bin/genltl.cc

@@ -260,11 +260,11 @@ static const argp_option options[] =
     { "go-theta", OPT_GO_THETA, "RANGE", 0,
       "!((GF(p1)&GF(p2)&...&GF(pn)) -> G(q->F(r)))", 0 },
     { "kr-n", OPT_KR_N, "RANGE", 0,
-      "formula of linear size with doubly exponential DBA", 0 },
+      "linear formula with doubly exponential DBA", 0 },
     { "kr-nlogn", OPT_KR_NLOGN, "RANGE", 0,
-      "forumla of n log n size with doubly exponential DBA", 0 },
+      "quasilinear formula with doubly exponential DBA", 0 },
     { "kv-phi", OPT_KV_PHI, "RANGE", 0,
-      "forumla of quadratic size with doubly exponential DBA", 0 },
+      "quadratic formula with doubly exponential DBA", 0 },
     OPT_ALIAS(kr-n2),
     { "or-fg", OPT_OR_FG, "RANGE", 0, "FG(p1)|FG(p2)|...|FG(pn)", 0 },
     OPT_ALIAS(ccj-xi),