* src/symtab.h (SUNDEF): New.

* src/symtab.c (bucket_new): Init user_token_number to SUNDEF to
stand for `uninitialized', instead of 0.
* src/reader.c (packsymbols, parse_thong_decl): Adjust.
* src/lex.c (lex): Adjust.
* tests/calc.at (_AT_DATA_CALC_Y): Declare a token for EOF.
Number it 0.
Let yylex return it instead of a plain 0.
Reported by Dick Streefland.

tests/calc.at

@@ -64,7 +64,8 @@ static void yyungetc (int c);
 extern void perror (const char *s);
 %}
 
-/* BISON Declarations */
+/* Bison Declarations */
+%token CALC_EOF 0
 %token NUM
 
 %nonassoc '=' /* comparison	       */
@@ -204,7 +205,7 @@ yylex (void)
 
   /* Return end-of-file.  */
   if (c == EOF)
-    return 0;
+    return CALC_EOF;
 
   /* Return single chars. */
   return c;