traces: show the stack after reading a token

Currently, if we have long rules and series of shift, we stack states
without showing stack.  Let's be more incremental, and do how the Java
skeleton does.

* data/skeletons/lalr1.cc, data/skeletons/lalr1.d,
* data/skeletons/yacc.c:
Here.
Adjust test cases.
* tests/torture.at (AT_DATA_STACK_TORTURE): Disable stack traces: this
test produces a very large stack, and showing the stack each time we
shift a token goes quadatric.

data/skeletons/lalr1.cc

@@ -854,6 +854,7 @@ b4_dollar_popdef])[]dnl
   `-----------------------------------------------*/
   yynewstate:
     YYCDEBUG << "Entering state " << int (yystack_[0].state) << '\n';
+    YY_STACK_PRINT ();
 
     // Accept?
     if (yystack_[0].state == yyfinal_)

data/skeletons/lalr1.d

@@ -476,7 +476,9 @@ m4_popdef([b4_at_dollar])])dnl
         /* New state.  Unlike in the C/C++ skeletons, the state is already
            pushed when we come here.  */
       case YYNEWSTATE:]b4_parse_trace_if([[
-        yycdebugln (format("Entering state %d", yystate));]])[
+        yycdebugln (format("Entering state %d", yystate));
+        if (0 < yydebug)
+          yystack.print (yyDebugStream);]])[
 
         /* Accept?  */
         if (yystate == yyfinal_)

data/skeletons/yacc.c

@@ -1596,6 +1596,7 @@ yysetstate:
   YY_IGNORE_USELESS_CAST_BEGIN
   *yyssp = YY_CAST (yy_state_t, yystate);
   YY_IGNORE_USELESS_CAST_END
+  YY_STACK_PRINT (yyss, yyssp);
 
   if (yyss + yystacksize - 1 <= yyssp)
 #if !defined yyoverflow && !defined YYSTACK_RELOCATE