Currently the example really looks like C. Instead of a union of
structs to implement the AST, use a hierarchy. It would be nice to
feature a C++17 version with std variants.
* examples/c++/glr/c++-types.yy (Node, free_node, new_nterm)
(new_term): Move into...
* examples/c++/glr/ast.hh: here, a proper C++ hierarchy.
Currently this example crashes on input such as "T (x) + y;".
The same example with glr.c works properly.
* examples/c++/glr/Makefile, examples/c++/glr/README.md,
* examples/c++/glr/c++-types.test, examples/c++/glr/c++-types.yy,
* examples/c++/glr/local.mk, examples/c++/local.mk: New.
Based on examples/c/glr/c++-types.y.
