Improve C++ namespace support. Discussed starting at

<http://lists.gnu.org/archive/html/help-bison/2007-09/msg00016.html>.
* data/c++.m4: (b4_namespace_ref, b4_namespace_open,
b4_namespace_close): New macros that interpret the %define variable
"namespace" so its value can contain "::" to indicate nested
namespaces.
* data/glr.cc (b4_namespace): Don't define, and replace all uses with
the above macros.
* data/lalr1.cc (b4_namespace): Likewise.
* data/location.cc (b4_namespace): Likewise.
* doc/bison.texinfo (Decl Summary): Move `%define push_pull' entry
inside a new table in the general %define entry.  Document `%define
namespace' there as well.  Point the %name-prefix entry to it since it
explains it more completely in the case of C++.
(C++ Bison Interface): Mention `%define namespace' instead of
%name-prefix.
(Table of Symbols): Remove the `%define push_pull' entry.  The %define
entry suffices.
* tests/c++.at (Relative namespace references): New test case.
(Absolute namespace references): New test case.
(Syntactically invalid namespace references): New test case.
* tests/input.at (C++ namespace reference errors): New test case.

data/location.cc

@@ -25,7 +25,7 @@ b4_copyright([Positions for Bison parsers in C++],
 
 /**
  ** \file position.hh
- ** Define the ]b4_percent_define_get([[namespace]])[::position class.
+ ** Define the ]b4_namespace_ref[::position class.
  */
 
 #ifndef BISON_POSITION_HH
@@ -35,8 +35,7 @@ b4_copyright([Positions for Bison parsers in C++],
 # include <string>
 # include <algorithm>
 
-namespace ]b4_percent_define_get([[namespace]])[
-{
+]b4_namespace_open[
   /// Abstract a position.
   class position
   {
@@ -142,7 +141,7 @@ namespace ]b4_percent_define_get([[namespace]])[
     return ostr << pos.line << '.' << pos.column;
   }
 
-}
+]b4_namespace_close[
 #endif // not BISON_POSITION_HH]
 @output(b4_dir_prefix[]location.hh@)
 b4_copyright([Locations for Bison parsers in C++],
@@ -150,7 +149,7 @@ b4_copyright([Locations for Bison parsers in C++],
 
 /**
  ** \file location.hh
- ** Define the ]b4_percent_define_get([[namespace]])[::location class.
+ ** Define the ]b4_namespace_ref[::location class.
  */
 
 #ifndef BISON_LOCATION_HH
@@ -160,8 +159,7 @@ b4_copyright([Locations for Bison parsers in C++],
 # include <string>
 # include "position.hh"
 
-namespace ]b4_percent_define_get([[namespace]])[
-{
+]b4_namespace_open[
 
   /// Abstract a location.
   class location
@@ -270,7 +268,7 @@ namespace ]b4_percent_define_get([[namespace]])[
     return ostr;
   }
 
-}
+]b4_namespace_close[
 
 #endif // not BISON_LOCATION_HH]
 m4_divert_pop(0)