Add function compilation

Functions are compiled in the most naiive way right now. I want to fix
up how scope lookups are done before it becomes too much to update.

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

src/obj/fun.rs

@@ -18,11 +18,11 @@ pub struct UserFun {
     code: Vec<Inst>,
     // Safe because this is just an interner that points to symbols, which aren't GC'd
     #[shredder(unsafe_skip)]
-    locals: Names,
+    locals: Locals,
 }
 
 impl UserFun {
-    pub fn new_obj(code: Vec<Inst>, locals: Names) -> UserFunRef {
+    pub fn new_obj(code: Vec<Inst>, locals: Locals) -> UserFunRef {
         let obj_ref = ObjRef::new(UserFun {
             vtable: Default::default(), // this is a placeholder for the real vtable
             attrs: Default::default(),
@@ -47,7 +47,7 @@ impl UserFun {
         &self.code
     }
 
-    pub fn locals(&self) -> &Names {
+    pub fn locals(&self) -> &Locals {
         &self.locals
     }
 }