Simplify union and prologue handling, and escape union and lex/parse

params with digraphs.
* data/bison.m4 (b4_pre_prologue, b4_post_prologue): Set their default
values to the empty string since these are no longer guaranteed
initialized by the front-end.
* data/glr.c, data/glr.cc, data/lalr1.cc, data/push.c, data/yacc.c: Add
braces around b4_user_stype since this is no longer done by the
front-end.
* src/files.c, src/files.h (pre_prologue_obstack,
post_prologue_obstack): Remove.
* src/muscle_tab.c (muscle_pair_list_grow): Don't duplicate header
comments here.  Use MUSCLE_OBSTACK_SGROW so that values are escaped
with digraphs.  This fixes lex params and parse params.
* src/muscle_tab.h (muscle_pair_list_grow): Update comments.
* src/output.c (prepare): Remove muscle insertion of the prologues.
(output): Remove freeing of pre_prologue_obstack and
post_prologue_obstack.
* src/parse-gram.y (prologue_declaration): Use muscle_code_grow rather
than prologue_augment for prologue parsing so you don't need prologue
obstacks.
(grammar_declaration): Use `braceless' instead of "{...}" so that
braces are already stripped and code is escaped with digraphs.
* src/reader.c (prologue_augment): Remove.
(reader): Remove initialization of pre_prologue_obstack and
post_prologue_obstack.
* src/reader.h (prologue_augment): Remove.

* data/c.m4: Remove stray parenthesis.

data/bison.m4

@@ -155,6 +155,8 @@ m4_define([b4_fatal_at],
 ## ---------------- ##
 
 # m4_define_default([b4_lex_param], [])   dnl breaks other skeletons
+m4_define_default([b4_pre_prologue], [])
+m4_define_default([b4_post_prologue], [])
 m4_define_default([b4_epilogue], [])
 m4_define_default([b4_parse_param], [])
 

data/c.m4

@@ -79,7 +79,7 @@ m4_define([b4_user_args],
 # If defined, b4_parse_param arrives double quoted, but below we prefer
 # it to be single quoted.
 m4_define([b4_parse_param],
-b4_parse_param))
+b4_parse_param)
 
 
 # b4_parse_param_for(DECL, FORMAL, BODY)

data/glr.c

@@ -180,8 +180,9 @@ b4_token_enums(b4_tokens)
 [#ifndef YYSTYPE
 ]m4_ifdef([b4_stype],
 [[typedef union ]b4_union_name[
+{
 ]b4_user_stype[
-	YYSTYPE;
+} YYSTYPE;
 # define YYSTYPE_IS_TRIVIAL 1]],
 [m4_if(b4_tag_seen_flag, 0,
 [[typedef int YYSTYPE;

data/glr.cc

@@ -280,8 +280,9 @@ namespace ]b4_namespace[
 #ifndef YYSTYPE
 ]m4_ifdef([b4_stype],
 [    union semantic_type
+    {
 b4_user_stype
-	;],
+    };],
 [m4_if(b4_tag_seen_flag, 0,
 [[    typedef int semantic_type;]],
 [[    typedef YYSTYPE semantic_type;]])])[

data/lalr1.cc

@@ -108,8 +108,9 @@ namespace ]b4_namespace[
 #ifndef YYSTYPE
 ]m4_ifdef([b4_stype],
 [    union semantic_type
+    {
 b4_user_stype
-	;],
+    };],
 [m4_if(b4_tag_seen_flag, 0,
 [[    typedef int semantic_type;]],
 [[    typedef YYSTYPE semantic_type;]])])[

data/push.c

@@ -205,8 +205,9 @@ b4_token_enums_defines(b4_tokens)[
 #if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
 ]m4_ifdef([b4_stype],
 [[typedef union ]b4_union_name[
+{
 ]b4_user_stype[
-	YYSTYPE;
+} YYSTYPE;
 # define YYSTYPE_IS_TRIVIAL 1]],
 [m4_if(b4_tag_seen_flag, 0,
 [[typedef int YYSTYPE;
@@ -1660,8 +1661,9 @@ b4_token_enums_defines(b4_tokens)
 [#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
 ]m4_ifdef([b4_stype],
 [[typedef union ]b4_union_name[
+{
 ]b4_user_stype[
-	YYSTYPE;
+} YYSTYPE;
 # define YYSTYPE_IS_TRIVIAL 1]],
 [m4_if(b4_tag_seen_flag, 0,
 [[typedef int YYSTYPE;

data/yacc.c

@@ -192,8 +192,9 @@ b4_token_enums_defines(b4_tokens)[
 #if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
 ]m4_ifdef([b4_stype],
 [[typedef union ]b4_union_name[
+{
 ]b4_user_stype[
-	YYSTYPE;
+} YYSTYPE;
 # define YYSTYPE_IS_TRIVIAL 1]],
 [m4_if(b4_tag_seen_flag, 0,
 [[typedef int YYSTYPE;
@@ -1497,8 +1498,9 @@ b4_token_enums_defines(b4_tokens)
 [#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
 ]m4_ifdef([b4_stype],
 [[typedef union ]b4_union_name[
+{
 ]b4_user_stype[
-	YYSTYPE;
+} YYSTYPE;
 # define YYSTYPE_IS_TRIVIAL 1]],
 [m4_if(b4_tag_seen_flag, 0,
 [[typedef int YYSTYPE;