Remove quotes from variables names in %define directives and from

qualifiers in %code directives, and restrict the characters that are
allowed in them to M4-friendly ones.  For %define, continue to support
the quoted form as a deprecated feature.  Discussed starting at
<http://lists.gnu.org/archive/html/bison-patches/2007-01/msg00023.html>.
* NEWS (2.3a+): Add entry for the change to %define.  Update entry for
%code.
* doc/bison.texinfo (Prologue Alternatives): Update.
(Bison Declaration Summary): In %defines entry, update mention of
`%code requires' and `%code provides'.
(C++ Location Values): Update %define uses.
(Calc++ Parser Interface): Likewise.
(Calc++ Parser): Likewise, and update `%code requires' uses.
(Bison Symbols): Update %code documentation.
* src/parse-gram.y (prologue_declaration): For %define variables, use
`variable' instead of `STRING'.
(grammar_declaration): For %code qualifiers, use `ID' instead of
`STRING'.
(variable): New nonterminal that takes an `ID' or a `STRING'.
* tests/actions.at (_AT_CHECK_PRINTER_AND_DESTRUCTOR): Update %code
and %define uses.
* tests/calc.at (_AT_DATA_CALC_Y): Update %define use.
* tests/input.at (Reject unused %code qualifiers): Update %code uses.
(%define errors): Update %define uses.

src/parse-gram.y

@@ -190,9 +190,9 @@ static int current_prec = 0;
 %printer { fprintf (stderr, "{\n%s\n}", $$); }
 	 braceless content.opt "{...}" "%{...%}" EPILOGUE
 
-%type <uniqstr> TYPE ID ID_COLON
+%type <uniqstr> TYPE ID ID_COLON variable
 %printer { fprintf (stderr, "<%s>", $$); } TYPE
-%printer { fputs ($$, stderr); } ID
+%printer { fputs ($$, stderr); } ID variable
 %printer { fprintf (stderr, "%s:", $$); } ID_COLON
 
 %type <integer> INT
@@ -232,10 +232,8 @@ prologue_declaration:
       code_scanner_last_string_free ();
     }
 | "%debug"                         { debug_flag = true; }
-| "%define" STRING content.opt
+| "%define" variable content.opt
     {
-      /* FIXME: Special characters in $2 may break %define.
-         For example: `['.  */
       char const name_prefix[] = "percent_define_";
       char *name = xmalloc (sizeof name_prefix + strlen ($2));
       strcpy (name, name_prefix);
@@ -326,10 +324,8 @@ grammar_declaration:
       muscle_code_grow ("percent_code", $2, @2);
       code_scanner_last_string_free ();
     }
-| "%code" STRING braceless
+| "%code" ID braceless
     {
-      /* FIXME: Special characters in $2 may break %code.
-         For example: `['.  */
       char const name_prefix[] = "percent_code_";
       char *name = xmalloc (sizeof name_prefix + strlen ($2));
       strcpy (name, name_prefix);
@@ -535,9 +531,14 @@ rhs:
 ;
 
 
-/*---------------*
- | content.opt.  |
- *--------------*/
+/*----------------------------*
+ | variable and content.opt.  |
+ *---------------------------*/
+
+variable:
+  ID
+  | STRING { $$ = uniqstr_new ($1); } /* deprecated and not M4-friendly */
+  ;
 
 /* Some content or "1" by default. */
 content.opt: