Functions are implemented and VM should be able to handle function calls

* VM Signals are used by running functions to dictate whether a function
  should return, or if it should call another function. These signals
  can be injected at any time allowing for user functions to inject
  themselves at runtime.
* obj::Method is gone since it's not being used yet.
* Obj impls must implement as_any(&self) -> &dyn Any now. This allows
  for UserFun and NativeFun to be explicitly cast (among other things,
  in the future).

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

src/vm/package.rs

@@ -1,8 +1,9 @@
 use crate::{obj::prelude::*, vm::{consts::ConstPool, inst::Inst}};
+use shredder::Scan;
 use std::io::{self, Write};
 
 /// A compiled package that can be executed by a VM.
-#[derive(Debug)]
+#[derive(Scan, Debug)]
 pub struct Package {
     names: Vec<Sym>, // local names mappings
     const_pool: ConstPool,
@@ -31,6 +32,7 @@ impl Package {
         &self.code
     }
 
+    /// Dumps a debug output of this package to the given writer.
     pub fn dump(&self, writer: &mut dyn Write) -> io::Result<()> {
         // column widths
         let addr_w = num_digits(self.code().len(), 16).max(4);
@@ -48,9 +50,6 @@ impl Package {
                     {
                         let obj_ref = self.const_pool().get(*hdl);
                         read_obj!(let obj = obj_ref);
-                        // XXX weirdness with coercion, can't deref as a &dyn Obj because
-                        // RwReadLockGuard is not Obj - but using Deref::deref works
-                        let obj: &dyn Obj = std::ops::Deref::deref(obj);
                         format!("{:?}", obj)
                     },
                 ),