Remove MetaMethod and GhostMethod (#1705)

RDoc has no special handling for these. `MetaMethod` is unreferenced,
and `GhostMethod` was only used for tomdoc.

Author: Earlopain

lib/rdoc.rb

@@ -197,8 +197,6 @@ def self.home
   autoload :Alias,          "#{__dir__}/rdoc/code_object/alias"
   autoload :AnyMethod,      "#{__dir__}/rdoc/code_object/any_method"
   autoload :MethodAttr,     "#{__dir__}/rdoc/code_object/method_attr"
-  autoload :GhostMethod,    "#{__dir__}/rdoc/code_object/ghost_method"
-  autoload :MetaMethod,     "#{__dir__}/rdoc/code_object/meta_method"
   autoload :Attr,           "#{__dir__}/rdoc/code_object/attr"
 
   autoload :Constant,       "#{__dir__}/rdoc/code_object/constant"

lib/rdoc/code_object.rb

@@ -16,8 +16,6 @@
 # * RDoc::MethodAttr
 #   * RDoc::Attr
 #   * RDoc::AnyMethod
-#     * RDoc::GhostMethod
-#     * RDoc::MetaMethod
 # * RDoc::Alias
 # * RDoc::Constant
 # * RDoc::Require

lib/rdoc/code_object/ghost_method.rb

@@ -308,7 +308,7 @@ def parse_comment_tomdoc(container, comment, line_no, start_line)
 
     name, = signature.split %r%[ \(]%, 2
 
-    meth = RDoc::GhostMethod.new comment.text, name
+    meth = RDoc::AnyMethod.new comment.text, name
     record_location(meth)
     meth.line = start_line
     meth.call_seq = signature