Improve tests for stack overflow in GLR parser.

Problem reported by twlevo@xs4all.nl.
* data/glr.c (struct yyGLRStack): Remove yyerrflag member.
All uses removed.
(yyStackOverflow): Just longjmp, but with value 2 so that caller
can handle the problem.
(YYCHK1): Use goto (a la yacc.c) rather than setting a flag.
(yyparse): New local variable yyresult to record the result.
Use result of setjmp to set it, rather than storing itinto
struct.
(yyDone): Remove label.
(yyacceptlab, yyabortlab, yyoverflowlab, yyreturn): New labels,
to mimic yacc.c.  Do not discard lookahead if it's EOF (possible
if YYABORT is used).
* tests/actions.at (_AT_CHECK_PRINTER_AND_DESTRUCTOR): Exit with
yyparse status; put status > 1 into diagnostic.
Check that status==2 works.
* tests/calc.at, tests/cxx-type.at, tests/glr-regression.at:
Use exit status 3 for failure to open (which shouldn't happen).

tests/actions.at

@@ -337,16 +337,18 @@ yyerror (const char *msg)
 int
 main (int argc, const char *argv[])
 {
+  int status;
   yydebug = !!getenv ("YYDEBUG");
   assert (argc == 2);
   yysource = argv[1];
-  if (yyparse ())
+  status = yyparse ();
+  switch (status)
     {
-      printf ("Parsing FAILED.\n");
-      exit (1);
+      case 0: printf ("Successful parse.\n"); break;
+      case 1: printf ("Parsing FAILED.\n"); break;
+      default: printf ("Parsing FAILED (status %d).\n", status); break;
     }
-  printf ("Successful parse.\n");
-  return 0;
+  return status;
 }
 ]])
 
@@ -450,7 +452,7 @@ Parsing FAILED.
 # Upon stack overflow, all symbols on the stack should be destroyed.
 # Only check for yacc.c.
 AT_YACC_IF([
-AT_PARSER_CHECK([./input '(x)(x)(x)(x)(x)(x)(x)'], 1,
+AT_PARSER_CHECK([./input '(x)(x)(x)(x)(x)(x)(x)'], 2,
 [[sending: '(' (0@0-9)
 sending: 'x' (1@10-19)
 thing (1@10-19): 'x' (1@10-19)
@@ -493,7 +495,7 @@ Freeing nterm line (9@90-119)
 Freeing nterm line (6@60-89)
 Freeing nterm line (3@30-59)
 Freeing nterm line (0@0-29)
-Parsing FAILED.
+Parsing FAILED (status 2).
 ]])
 ])
 

tests/calc.at

@@ -288,7 +288,7 @@ power (int base, int exponent)
 {
   int res = 1;
   if (exponent < 0)
-    exit (1);
+    exit (3);
   for (/* Niente */; exponent; --exponent)
     res *= base;
   return res;
@@ -315,7 +315,7 @@ main (int argc, const char **argv)
   if (!yyin)
     {
       perror (argv[1]);
-      exit (1);
+      return 3;
     }
 
 ]AT_LALR1_CC_IF([], [m4_bmatch([$4], [%debug],

tests/cxx-type.at

@@ -115,8 +115,8 @@ main (int argc, char **argv)
   if (argc != 2)
     abort ();
   if (!freopen (argv[1], "r", stdin))
-    abort ();
-  exit (yyparse ());
+    return 3;
+  return yyparse ();
 }
 
 int

tests/glr-regression.at

@@ -202,7 +202,7 @@ int
 main (int argc, char **argv)
 {
   yyin = stdin;
-  if (argc == 2 && !(yyin = fopen (argv[1], "r"))) return 1;
+  if (argc == 2 && !(yyin = fopen (argv[1], "r"))) return 3;
   return yyparse ();
 }
 ]])
@@ -312,7 +312,7 @@ int yylex (void)
 
 int main(int argc, char* argv[]) {
   yyin = stdin;
-  if (argc == 2 && !(yyin = fopen (argv[1], "r"))) return 1;
+  if (argc == 2 && !(yyin = fopen (argv[1], "r"))) return 3;
   return yyparse ();
 }
 ]])