Add include for toplevel self(main)
add dummy visibility methods (public/protected/private) that do nothing; ref #1357
Merge branch 'toplevel_ext' of https://github.com/kyab/mruby into kyab-toplevel_ext
add private/protected/public to main
add mruby-toplevel-ext as default
Merge branch 'kyab-toplevel_ext'
Replace mrb_intern() with mrb_intern_cstr().
Merge pull request #1363 from suzukaze/refactor-class.c

Replace mrb_intern() with mrb_intern_cstr().
factor out context stack marking
mark stacks in final_marking; close #1359; close #1362
Merge branch 'master' of github.com:mruby/mruby