Break out obj module into individual files by type

object.rs was getting a little big and the implementations are only
going to get bigger.

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

src/compile.rs

@@ -1,4 +1,4 @@
-use crate::obj::*;
+use crate::obj::prelude::*;
 use crate::scope::*;
 use crate::syn::ast::*;
 use crate::vm::inst::*;