rename meta to singleton class

seems more appropriate, as it is the class for a single object
Also seems to be called that on the net (don't remember where the meta came from, but it's gone)

lib/vool/class_expression.rb

@@ -37,7 +37,7 @@ module Vool
         when MethodExpression
           node.to_mom(@clazz)
         when ClassMethodExpression
-          node.to_mom(@clazz.meta_class)
+          node.to_mom(@clazz.singleton_class)
         else
           raise "Only methods for now #{node.class}:#{node}"
         end
@@ -62,7 +62,7 @@ module Vool
     end
 
     # goes through the code looking for instance variables (and their assignments)
-    # adding each to the respective type, ie class or meta_class, depending
+    # adding each to the respective type, ie class or singleton_class, depending
     # on if they are instance or class instance variables.
     #
     # Class variables are deemed a design mistake, ie not implemented (yet)
@@ -72,7 +72,7 @@ module Vool
         when MethodExpression
           target = @clazz
         when ClassMethodExpression
-          target = @clazz.meta_class
+          target = @clazz.singleton_class
         else
           raise "Only methods for now #{node.class}:#{node}"
         end

lib/vool/class_method_expression.rb

@@ -8,7 +8,7 @@ module Vool
     end
 
     def to_mom(clazz)
-      raise "not meta" unless clazz.class == Parfait::MetaClass
+      raise "not singleton" unless clazz.class == Parfait::SingletonClass
       raise( "no class in #{self}") unless clazz
       method = clazz.add_instance_method_for(name , make_arg_type , make_frame , body )
       #puts "CLass method Class:#{clazz}:#{name}"

lib/vool/variables.rb

@@ -49,7 +49,7 @@ module Vool
   class ModuleName < Expression
     include Named
     def ct_type
-      get_named_class.meta_class.instance_type
+      get_named_class.singleton_class.instance_type
     end
     def to_slot(_)
       return Mom::SlotDefinition.new( get_named_class, [])