* src/gram.h, src/gram.c (error_token_number): Remove, use

errtoken->number.
* src/reader.c (reader): Don't specify the user token number (2)
for $undefined, as it uselessly prevents using it.
* src/gram.h (token_number_t): Move to...
* src/symtab.h: here.
(state_t.number): Is a token_number_t.
* src/print.c, src/reader.c: Use undeftoken->number instead of
hard coded 2.
(Even though this 2 is not the same as above: the number of the
undeftoken remains being 2, it is its user token number which
might not be 2).
* src/output.c (prepare_tokens): Rename the `maxtok' muscle with
`user_token_number_max'.
Output `undef_token_number'.
* data/bison.simple, data/bison.c++: Use them.
Be sure to map invalid yylex return values to
`undef_token_number'.  This saves us from gratuitous SEGV.
* tests/conflicts.at (Solved SR Conflicts)
(Unresolved SR Conflicts): Adjust.
* tests/regression.at (Web2c Actions): Adjust.

data/bison.simple

@@ -1,4 +1,4 @@
-m4_divert(-1)
+m4_divert(-1)                                                       -*- C -*-
 
 # b4_sint_type(MAX)
 # -----------------
@@ -265,11 +265,14 @@ b4_token_defines(b4_tokens)
 #define YYNRULES  b4_nrules
 /* YYNRULES -- Number of states. */
 #define YYNSTATES  b4_nstates
-#define YYMAXUTOK  b4_maxtok
 
 /* YYTRANSLATE(YYLEX) -- Bison symbol number corresponding to YYLEX.  */
+#define YYUNDEFTOK  b4_undef_token_number
+#define YYMAXUTOK   b4_user_token_number_max
+
 typedef b4_uint_type(b4_token_number_max) yy_token_number_type;
-#define YYTRANSLATE(x) ((unsigned)(x) <= b4_maxtok ? yytranslate[[x]] : b4_nsym)
+#define YYTRANSLATE(X) \
+  ((unsigned)(X) <= YYMAXUTOK ? yytranslate[[X]] : YYUNDEFTOK)
 
 /* YYTRANSLATE[[YYLEX]] -- Bison symbol number corresponding to YYLEX.  */
 static const yy_token_number_type yytranslate[[]] =