Split up src/obj.rs

* common macros are in their own private module
* functions are in their own obj::function module

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 use std::rc::Rc;
 
+use crate::obj::function::*;
 use crate::obj::*;
 
 #[derive(Debug, Clone, Copy, PartialEq)]