glr2.cc: example: use objects (not pointers) to represent the AST

Currently we are using pointers.  The whole point of
glr2.cc (vs. glr.cc) is precisely to allow genuine C++ objects to be
semantic values.  Let's make that work.

* data/skeletons/glr2.cc (glr_state::glr_state): Be sure to initialize
yysval.
(glr_state): Add copy-ctor, assignment and dtor.
(glr_state::copyFrom): Be sure to initialize the destination if it was
not.
(glr_state::~glr_state): Destroy the semantic value.
* examples/c++/glr/ast.hh: Rewrite so that we use genuine objects,
rather than a traditional OOP hierarchy that requires to deal with
pointers.
With help from Bruno Belanyi <[email protected]>.
* examples/c++/glr/c++-types.yy: Remove memory management.
Use true objects.
(main): Don't reach yydebug directly.

* examples/c++/glr/local.mk: We need C++11.

THANKS

@@ -34,6 +34,7 @@ Bob Rossi                 [email protected]
 Brandon Lucia             [email protected]
 Brooks Moses              [email protected]
 Bruce Lilly               [email protected]
+Bruno Belanyi             [email protected]
 Bruno Haible              [email protected]
 Charles-Henri de Boysson  [email protected]
 Christian Burger          [email protected]