unify space collection attribute naming

currently space is still acting as a sort of memory manager.
For proper linking, all objects must be reachable from space, hence the plural versions like messages and addresses (even they are instances, it is the list that is important)
To dish out instance to use, the head must be kept, ie next_XXX for intergers, return addresses and messages

lib/risc/builtin/object.rb

@@ -51,9 +51,9 @@ module Risc
           builder = compiler.compiler_builder(compiler.method)
           builder.build do
             space << Parfait.object_space
-            message << space[:first_message]
+            message << space[:next_message]
             next_message << message[:next_message]
-            space[:first_message] << next_message
+            space[:next_message] << next_message
           end
 
           Mom::MessageSetup.new(Parfait.object_space.get_main).build_with( builder )

lib/risc/parfait_boot.rb

@@ -141,9 +141,10 @@ module Parfait
         Object: {},
         BinaryCode: {next: :BinaryCode} ,
         Space: {classes: :Dictionary , types: :Dictionary ,
-                first_message: :Message , next_integer: :Integer ,
-                true_object: :TrueClass, next_address: :ReturnAddress ,
-                false_object: :FalseClass , nil_object: :NilClass},
+                next_message: :Message , messages: :Message ,
+                next_integer: :Integer,  integers: :Integer ,
+                next_address: :ReturnAddress ,addresses: :ReturnAddress ,
+                true_object: :TrueClass, false_object: :FalseClass , nil_object: :NilClass},
         NamedList: {},
         Type: {names: :List , types: :List  ,
                object_class: :Class, methods: :TypedMethod } ,