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/compiler.rs

@@ -8,6 +8,7 @@ use common_macros::hash_map;
 use thiserror::Error;
 
 use crate::ast::*;
+use crate::obj::function::UserFunctionInst;
 use crate::obj::*;
 use crate::token::TokenKind;
 use crate::vm::*;