Ruby

• class.c: refactored singleton class related matters.
  Handles eigenclasses and plain classes transparently.

  (make_metaclass): renamed from make_metametaclass.
  (METACLASS_OF): new utility macro
  (META_CLASS_OF_CLASS_CLASS): ditto.
  (ENSURE_EIGENCLASS): ditto.
  (make_singleton_class): extracted from rb_singleton_class.
  (boot_defclass): moved from object.c
  (Init_class_hierarchy): extracted from Init_Object.
  (rb_make_metaclass): refactored.
  (singleton_class_of): extracted from rb_singleton_class.
  (rb_singleton_class): refactored.
  (rb_define_singleton_method): it needs a metaclass only
  but not its metametaclass.

• object.c: booting class hierarchy was moved to class.c
  for keeping dependency between compilation units least.
  (Init_Object): extracting the booting into
  Init_class_hierarchy.
  (boot_defclass): moved to class.c.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24720 b2dd03c8-39d4-4d8f-98ff-823fe69b080e