Set all front-end %define defaults in one place.

* src/main.c (main): Move lr.keep_unreachable_states default...
* src/reader.c (reader): ... to here.
(cherry picked from commit 1c4aa81df1)

src/main.c

@@ -114,7 +114,6 @@ main (int argc, char *argv[])
      declarations.  */
   timevar_push (TV_CONFLICTS);
   conflicts_solve ();
-  muscle_percent_define_default ("lr.keep_unreachable_states", "false");
   if (!muscle_percent_define_flag_if ("lr.keep_unreachable_states"))
     {
       state_number *old_to_new = xnmalloc (nstates, sizeof *old_to_new);