Request: Add version number in header files

[marcalff]

Please add version numbers in header files, that can be used at compile time.

For example:

#define RYML_VERSION "0.7.0"
#define RYML_VERSION_MAJOR 0
#define RYML_VERSION_MINOR 7
#define RYML_VERSION_PATCH 0

This helps when code using ryml needs to be different for v0.6.0 and v0.7.0, due to api breaking changes.

To illustrate, right now my application code looks like:

  ryml::ParserOptions opts;
  opts.locations(true);

#if OTEL_HAVE_RYML == 6
  ryml::Parser parser(opts);
#endif

#if OTEL_HAVE_RYML == 7
  ryml::Parser::handler_type event_handler;
  ryml::Parser parser(&event_handler, opts);
#endif

  ryml::Tree tree;
  ryml::csubstr filename;
  ryml::csubstr csubstr_content;
  std::unique_ptr<Document> doc;

  filename        = ryml::to_csubstr(source);
  csubstr_content = ryml::to_csubstr(content);

  try
  {
#if OTEL_HAVE_RYML == 6
    tree = parser.parse_in_arena(filename, csubstr_content);
#endif

#if OTEL_HAVE_RYML == 7
    tree = parse_in_arena(&parser, filename, csubstr_content);
#endif

    tree.resolve();
  }
  catch (...)

where OTEL_HAVE_RYML is evaluated by CMake, based on what find_package() actually found.

It is desirable to rely on RYML_VERSION_MAJOR, RYML_VERSION_MINOR and RYML_VERSION_PATCH found in the ryml header files instead.