doc: promote yytoken_kind_t, not yytokentype

* data/skeletons/c.m4 (yytoken_kind_t): New.
* data/skeletons/c++.m4, data/skeletons/lalr1.cc (yysymbol_kind_type):
New.
* examples/c/lexcalc/parse.y, examples/c/reccalc/parse.y,
* tests/regression.at:
Use them.
* doc/bison.texi: Replace "enum yytokentype" by "yytoken_kind_t".
(api.token.raw): Explain that it forces "yytoken_kind_t" to coincide
with "yysymbol_kind_t".
(Calling Convention): Mention YYEOF.
(Table of Symbols): Add entries for "yytoken_kind_t" and
"yysymbol_kind_t".
(Glossary): Add entries for "Kind", "Token kind" and "Symbol kind".

src/parse-gram.h

@@ -72,7 +72,7 @@ extern int gram_debug;
   } value_type;
 
 
-/* Token type.  */
+/* Token kinds.  */
 #ifndef GRAM_TOKENTYPE
 # define GRAM_TOKENTYPE
   enum gram_tokentype
@@ -139,6 +139,7 @@ extern int gram_debug;
     PERCENT_UNION = 59,            /* "%union"  */
     PERCENT_EMPTY = 60             /* "%empty"  */
   };
+  typedef enum gram_tokentype gram_token_kind_t;
 #endif
 
 /* Value type.  */