api.prefix.

* data/c.m4 (b4_api_prefix, b4_api_PREFIX): New.
(b4_prefix, b4_union_name, b4_token_enums, b4_declare_yylstype): Use them.
* data/glr.c, data/yacc.c, data/glr.cc, data/lalr1.cc: Use them to change
the prefix of exported preprocessor symbols.
* src/getargs.c (usage): Ditto.
* tests/headers.at (Several parsers): New.
* tests/local.at (AT_API_PREFIX): New.
AT_YYSTYPE, AT_YYLTYPE): Adjust.
* doc/bison.texi (Multiple Parsers): Move documentation of %name-prefix to...
(Table of Symbols): here.
(Multiple Parsers): Document api.prefix.
(%define Summary): Point to it.
Use @code for variable names.
(Bison Options): -p/--name-prefix are obsoleted.
* NEWS: Announce api.prefix.

data/glr.cc

@@ -269,7 +269,7 @@ b4_copyright([Skeleton interface for Bison GLR parsers in C++],
   {
   public:
     /// Symbol semantic values.
-#ifndef YYSTYPE
+#ifndef ]b4_api_PREFIX[STYPE
 ]m4_ifdef([b4_stype],
 [    union semantic_type
     {
@@ -277,9 +277,9 @@ b4_user_stype
     };],
 [m4_if(b4_tag_seen_flag, 0,
 [[    typedef int semantic_type;]],
-[[    typedef YYSTYPE semantic_type;]])])[
+[[    typedef ]b4_api_PREFIX[STYPE semantic_type;]])])[
 #else
-    typedef YYSTYPE semantic_type;
+    typedef ]b4_api_PREFIX[STYPE semantic_type;
 #endif
     /// Symbol locations.
     typedef ]b4_percent_define_get([[location_type]],
@@ -350,11 +350,11 @@ b4_user_stype
 b4_percent_define_flag_if([[global_tokens_and_yystype]],
 [b4_token_defines(b4_tokens)])
 [
-#ifndef YYSTYPE
-# define YYSTYPE ]b4_namespace_ref[::]b4_parser_class_name[::semantic_type
+#ifndef ]b4_api_PREFIX[STYPE
+# define ]b4_api_PREFIX[STYPE ]b4_namespace_ref[::]b4_parser_class_name[::semantic_type
 #endif
-#ifndef YYLTYPE
-# define YYLTYPE ]b4_namespace_ref[::]b4_parser_class_name[::location_type
+#ifndef ]b4_api_PREFIX[LTYPE
+# define ]b4_api_PREFIX[LTYPE ]b4_namespace_ref[::]b4_parser_class_name[::location_type
 #endif
 
 ]b4_namespace_close[