Redo some of the previous commit: add back the ability to use

non-aliased/undeclared string literals since it might be useful to
those declaring %token-table.
* src/reader.c (check_and_convert_grammar): Undo changes in previous
commit: don't worry about complaints from symbols_pack.
* src/symtab.c (symbol_new, symbol_class_set,
symbol_check_alias_consistency): Undo changes in previous commit: count         each string literal as a new symbol and token, assign it a symbol
number, and don't complain about non-aliased string literals.
(symbols_pack): Since symbol_make_alias still does not decrement symbol
and token counts but does still set aliased tokens to the same number,
symbol_pack_processor now leaves empty slots in the symbols array.
Remove those slots.
* tests/regression.at (Undeclared string literal): Remove test case
added in previous commit since non-aliased string literals are allowed
again.
(Characters Escapes, Web2c Actions): Undo changes in previous commit:
remove unnecessary string literal declarations.
* tests/sets.at (Firsts): Likewise.

tests/regression.at

@@ -489,9 +489,7 @@ AT_DATA_GRAMMAR([input.y],
 void yyerror (const char *s);
 int yylex (void);
 %}
-[%token QUOTES "\""
-%token TICK "'"
-%%
+[%%
 exp:
   '\'' "\'"
 | '\"' "\""
@@ -702,10 +700,6 @@ statement:  struct_stat;
 struct_stat:  /* empty. */ | if else;
 if: "if" "const" "then" statement;
 else: "else" statement;
-%token IF "if";
-%token CONST "const";
-%token THEN "then";
-%token ELSE "else";
 %%
 ]])
 
@@ -1126,7 +1120,7 @@ AT_SETUP([String alias declared after use])
 # Bison once incorrectly asserted that the symbol number for either a token or
 # its alias was the highest symbol number so far at the point of the alias
 # declaration.  That was true unless the declaration appeared after their first
-# uses.
+# uses and other tokens appeared in between.
 
 AT_DATA([input.y],
 [[%%
@@ -1137,25 +1131,3 @@ start: 'a' "A" 'b';
 AT_CHECK([bison -t -o input.c input.y])
 
 AT_CLEANUP
-
-
-
-## --------------------------- ##
-## Undeclared string literal.  ##
-## --------------------------- ##
-
-AT_SETUP([Undeclared string literal])
-
-# Bison once allowed a string literal to be used in the grammar without any
-# declaration assigning it as an alias of another token.
-
-AT_DATA([input.y],
-[[%%
-start: "abc";
-]])
-
-AT_CHECK([bison -t -o input.c input.y], [1], [],
-[[input.y:2.8-12: "abc" undeclared
-]])
-
-AT_CLEANUP

tests/sets.at

@@ -196,7 +196,6 @@ AT_DATA([input.y],
 [[%nonassoc '<' '>'
 %left '+' '-'
 %right '^' '='
-%token EXP "exp"
 %%
 exp:
    exp '<' exp