yacc.c: use yysymbol_type_t instead of int for yytoken

Now that we have a proper type for internal symbol numbers, let's use
it.  More code needs conversion, e.g., printers and destructors, but
they are shared with glr.c, which is not ready yet for this change.

It will also help us deal with warnings such as (GCC9 on GNU/Linux):

    input.c: In function 'int yyparse()':
    input.c:475:37: error: enumeral and non-enumeral type in conditional expression [-Werror=extra]
      475 |   (0 <= (YYX) && (YYX) <= YYMAXUTOK ? yytranslate[YYX] : YYSYMBOL_YYUNDEF)
          |    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    input.c:1024:17: note: in expansion of macro 'YYTRANSLATE'
     1024 |       yytoken = YYTRANSLATE (yychar);
          |                 ^~~~~~~~~~~

* data/skeletons/yacc.c (yytranslate, yysymbol_name)
(yyparse_context_t, yyexpected_tokens, yypstate_expected_tokens)
(yysyntax_error_arguments):
Use yysymbol_type_t instead of int.

data/skeletons/yacc.c

@@ -637,7 +637,7 @@ union yyalloc
 
 /* YYTRANSLATE[TOKEN-NUM] -- Symbol number corresponding to TOKEN-NUM
    as returned by yylex.  */
-static const ]b4_int_type_for([b4_translate])[ yytranslate[] =
+static const yysymbol_type_t yytranslate[] =
 {
   ]b4_translate[
 };]])[
@@ -650,7 +650,7 @@ static const ]b4_int_type_for([b4_translate])[ yytranslate[] =
 #if ]b4_parse_error_case([simple], [b4_api_PREFIX[DEBUG || ]b4_token_table_flag], [[1]])[
 /* The user-facing name of the symbol whose (internal) number is
    YYSYMBOL.  No bounds checking.  */
-static const char *yysymbol_name (int yysymbol) YY_ATTRIBUTE_UNUSED;
+static const char *yysymbol_name (yysymbol_type_t yysymbol) YY_ATTRIBUTE_UNUSED;
 
 ]b4_parse_error_bmatch([simple\|verbose],
 [[/* YYTNAME[SYMBOL-NUM] -- String name of the symbol SYMBOL-NUM.
@@ -661,12 +661,12 @@ static const char *const yytname[] =
 };
 
 static const char *
-yysymbol_name (int yysymbol)
+yysymbol_name (yysymbol_type_t yysymbol)
 {
   return yytname[yysymbol];
 }]],
 [[static const char *
-yysymbol_name (int yysymbol)
+yysymbol_name (yysymbol_type_t yysymbol)
 {
   static const char *const yy_sname[] =
   {
@@ -1013,7 +1013,7 @@ do {                                                                     \
    any old *YYES other than YYESA.  */
 static int
 yy_lac (yy_state_t *yyesa, yy_state_t **yyes,
-        YYPTRDIFF_T *yyes_capacity, yy_state_t *yyssp, int yytoken)
+        YYPTRDIFF_T *yyes_capacity, yy_state_t *yyssp, yysymbol_type_t yytoken)
 {
   yy_state_t *yyes_prev = yyssp;
   yy_state_t *yyesp = yyes_prev;
@@ -1125,7 +1125,7 @@ typedef struct
   yy_state_t *yyesa;
   yy_state_t **yyes;
   YYPTRDIFF_T *yyes_capacity;]])])[
-  int yytoken;]b4_locations_if([[
+  yysymbol_type_t yytoken;]b4_locations_if([[
   YYLTYPE *yylloc;]])[
 } yyparse_context_t;
 
@@ -1137,10 +1137,10 @@ typedef struct
    YYARG up to YYARGN. */]b4_push_if([[
 static int
 yypstate_expected_tokens (yypstate *yyps,
-                          int yyarg[], int yyargn)]], [[
+                          yysymbol_type_t yyarg[], int yyargn)]], [[
 static int
 yyexpected_tokens (const yyparse_context_t *yyctx,
-                   int yyarg[], int yyargn)]])[
+                   yysymbol_type_t yyarg[], int yyargn)]])[
 {
   /* Actual size of YYARG. */
   int yycount = 0;
@@ -1193,7 +1193,7 @@ yyexpected_tokens (const yyparse_context_t *yyctx,
 /* Similar to the previous function.  */
 static int
 yyexpected_tokens (const yyparse_context_t *yyctx,
-                   int yyarg[], int yyargn)
+                   yysymbol_type_t yyarg[], int yyargn)
 {
   return yypstate_expected_tokens (yyctx->yyps, yyarg, yyargn);
 }]])[
@@ -1202,10 +1202,10 @@ yyexpected_tokens (const yyparse_context_t *yyctx,
 ]b4_parse_error_bmatch(
          [custom],
 [[/* The token type of the lookahead of this context.  */
-static int
+static yysymbol_type_t
 yyparse_context_token (const yyparse_context_t *yyctx) YY_ATTRIBUTE_UNUSED;
 
-static int
+static yysymbol_type_t
 yyparse_context_token (const yyparse_context_t *yyctx)
 {
   return yyctx->yytoken;
@@ -1316,7 +1316,7 @@ yytnamerr (char *yyres, const char *yystr)
 
 static int
 yysyntax_error_arguments (const yyparse_context_t *yyctx,
-                          int yyarg[], int yyargn)
+                          yysymbol_type_t yyarg[], int yyargn)
 {
   /* Actual size of YYARG. */
   int yycount = 0;
@@ -1383,7 +1383,7 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
   const char *yyformat = YY_NULLPTR;
   /* Arguments of yyformat: reported tokens (one for the "unexpected",
      one per "expected"). */
-  int yyarg[YYARGS_MAX];
+  yysymbol_type_t yyarg[YYARGS_MAX];
   /* Cumulated lengths of YYARG.  */
   YYPTRDIFF_T yysize = 0;
 
@@ -1576,7 +1576,7 @@ yyparse (]m4_ifset([b4_parse_param], [b4_formals(b4_parse_param)], [void])[)]])[
   /* The return value of yyparse.  */
   int yyresult;
   /* Lookahead token as an internal (translated) token number.  */
-  int yytoken = 0;
+  yysymbol_type_t yytoken = 0;
   /* The variables used to return semantic value and location from the
      action routines.  */
   YYSTYPE yyval;]b4_locations_if([[