Consolidate the 4 prologue alternative directives (%code, %requires,

%provides, and %code-top) into a single %code directive with an
optional qualifier field.  Discussed at
<http://lists.gnu.org/archive/html/bison-patches/2007-01/msg00012.html>.
* NEWS (2.3a+): Rewrite the existing entry for the prologue
alternatives.
* doc/bison.texinfo (Prologue Alternatives): Update.
(Decl Summary): Update to %code "requires" and %code "provides".
(Calc++ Parser): Update to %code "requires".
(Bison Symbols): Remove entries for %requires, %provides, and
%code-top.  Rewrite %code entry, and add a %code "QUALIFIER" entry.
* data/bison.m4 (b4_user_provides, b4_user_requires): Remove as these
are replaced by b4_percent_code_provides and b4_percent_code_requires,
which are skeleton-specific.
(b4_check_percent_code_qualifiers): New.  A skeleton can use this to
declare what %code qualifiers it supports and to complain if any other
qualifiers were used in the grammar.
* data/glr.cc: Update to use b4_user_code([b4_percent_code_requires])
and b4_user_code([b4_percent_code_provides]) in place of
b4_user_requires and b4_user_provides.
* data/glr.c, data/lalr1.cc, data/push.c, data/yacc.c: Likewise.
Add b4_user_code([b4_percent_code_top]) and
b4_user_code([b4_percent_code]).
Invoke b4_check_percent_code_qualifiers.
* src/parse-gram.y (PERCENT_CODE_TOP, PERCENT_PROVIDES,
PERCENT_REQUIRES): Remove.
(grammar_declaration): Remove RHS's for %code-top, %provides, and
%requires.  Rewrite the %code RHS as the unqualified form defining the
muscle b4_percent_code.  Add another RHS for the qualified %code form,
which defines muscles of the form b4_percent_code_QUALIFIER and the
b4_used_percent_code_qualifiers muscle.
* src/scan-gram.l (PERCENT_CODE_TOP, PERCENT_PROVIDES,
PERCENT_REQUIRES): Remove.
* tests/actions.at (_AT_CHECK_PRINTER_AND_DESTRUCTOR): Update to use
%code "requires" and %code "provides".
* tests/input.at (Reject bad %code qualifiers): New.

data/yacc.c

@@ -24,6 +24,7 @@ m4_divert(-1)                                                -*- C -*-
 b4_use_push_for_pull_if([m4_include(b4_pkgdatadir/[push.c])m4_exit])
 
 m4_include(b4_pkgdatadir/[c.m4])
+b4_check_percent_code_qualifiers([[requires]], [[provides]], [[top]])
 
 ## ---------------- ##
 ## Default values.  ##
@@ -152,6 +153,9 @@ b4_copyright([Skeleton implementation for Bison's Yacc-like parsers in C],dnl '
    USER NAME SPACE" below.  */
 
 ]b4_identification
+m4_ifdef([b4_percent_code_top],
+[[/* Copy the %code "top" blocks.  */
+]b4_user_code([b4_percent_code_top])])[]dnl
 m4_if(b4_prefix, [yy], [],
 [/* Substitute the variable and function names.  */
 #define yyparse b4_prefix[]parse
@@ -184,9 +188,9 @@ b4_locations_if([#define yylloc b4_prefix[]lloc])])[
 # define YYTOKEN_TABLE ]b4_token_table[
 #endif
 
-]m4_ifdef([b4_requires],
-[[/* Copy the %requires blocks.  */
-]b4_user_requires])[]dnl
+]m4_ifdef([b4_percent_code_requires],
+[[/* Copy the %code "requires" blocks.  */
+]b4_user_code([b4_percent_code_requires])])[]dnl
 
 b4_token_enums_defines(b4_tokens)[
 
@@ -216,14 +220,18 @@ typedef struct YYLTYPE
 # define YYLTYPE_IS_TRIVIAL 1
 #endif])
 
-m4_ifdef([b4_provides],
-[[/* Copy the %provides blocks.  */
-]b4_user_provides])[]dnl
+m4_ifdef([b4_percent_code_provides],
+[[/* Copy the %code "provides" blocks.  */
+]b4_user_code([b4_percent_code_provides])])[]dnl
 
 [/* Copy the second part of user declarations.  */
-]b4_user_post_prologue[
+]b4_user_post_prologue
+m4_ifdef([b4_percent_code],
+[[/* Copy the unqualified %code blocks.  */
+]b4_user_code([b4_percent_code])
+])[]dnl
 
-#ifdef short
+[#ifdef short
 # undef short
 #endif
 
@@ -1492,9 +1500,9 @@ b4_defines_if(
 b4_copyright([Skeleton interface for Bison's Yacc-like parsers in C],dnl '
   [1984, 1989, 1990, 2000, 2001, 2002, 2003, 2004, 2005, 2006])
 
-m4_ifdef([b4_requires],
-[[/* Copy the %requires blocks.  */
-]b4_user_requires])[]dnl
+m4_ifdef([b4_percent_code_requires],
+[[/* Copy the %code "requires" blocks.  */
+]b4_user_code([b4_percent_code_requires])])[]dnl
 
 b4_token_enums_defines(b4_tokens)
 
@@ -1532,7 +1540,7 @@ typedef struct YYLTYPE
 	   [extern YYLTYPE b4_prefix[]lloc;])
 )dnl b4_locations_if
 
-m4_ifdef([b4_provides],
-[[/* Copy the %provides blocks.  */
-]b4_user_provides])[]
+m4_ifdef([b4_percent_code_provides],
+[[/* Copy the %code "provides" blocks.  */
+]b4_user_code([b4_percent_code_provides])])[]
 ])dnl b4_defines_if