Invoke initialize from Ruby, not native code

JRuby does not expose the `initialize` method for a given Data
instance to native code, so there's no equivalent to calling
`rb_struct_initialize`. This change moves that initialization to
a Ruby `__send__` and removes the native stub method `init_data`.

Fixes broken JRuby `Data` logic after #692.

Author: headius

ext/psych/psych_to_ruby.c

@@ -28,12 +28,6 @@ static VALUE path2class(VALUE self, VALUE path)
     return rb_path_to_class(path);
 }
 
-static VALUE init_data(VALUE self, VALUE data, VALUE values)
-{
-    rb_struct_initialize(data, values);
-    return data;
-}
-
 void Init_psych_to_ruby(void)
 {
     VALUE psych     = rb_define_module("Psych");
@@ -43,7 +37,6 @@ void Init_psych_to_ruby(void)
     VALUE visitor   = rb_define_class_under(visitors, "Visitor", rb_cObject);
     cPsychVisitorsToRuby = rb_define_class_under(visitors, "ToRuby", visitor);
 
-    rb_define_private_method(cPsychVisitorsToRuby, "init_data", init_data, 2);
     rb_define_private_method(cPsychVisitorsToRuby, "build_exception", build_exception, 2);
     rb_define_private_method(class_loader, "path2class", path2class, 1);
 }

lib/psych/visitors/to_ruby.rb

@@ -219,9 +219,7 @@ def visit_Psych_Nodes_Mapping o
             revive_data_members(members, o)
           end
           data ||= allocate_anon_data(o, members)
-          values = data.members.map { |m| members[m] }
-          init_data(data, values)
-          data.freeze
+          data.__send__ :initialize, **members
           data
 
         when /^!ruby\/object:?(.*)?$/