General changes across the runtime crate in support of compile module

* Compile module is able to compile bytecode (or so it seems...)
* Runtime crate has had some new stuff added to it, mostly with objects
  and vtables. Still not 100% on the object method function call story,
  but I guess it'll be tackled when we get there.

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

src/compile/mod.rs

@@ -0,0 +1,74 @@
+pub mod thunk;
+pub mod error;
+
+use runtime::{obj::prelude::*, vm::consts::*};
+use std::collections::HashMap;
+
+pub struct Compile<'t> {
+    text: &'t str,
+    const_data: ConstData,
+}
+
+impl<'t> Compile<'t> {
+    pub fn new(text: &'t str) -> Self {
+        Compile { text, const_data: Default::default() }
+    }
+
+    pub fn text(&self) -> &'t str {
+        self.text
+    }
+
+    pub fn const_data(&self) -> &ConstData {
+        &self.const_data
+    }
+
+    pub fn const_data_mut(&mut self) -> &mut ConstData {
+        &mut self.const_data
+    }
+
+    /// Gets or inserts a static int reference.
+    pub fn const_int(&mut self, int: i64) -> (ConstHandle, IntRef) {
+        self.const_data_mut()
+            .const_int(int)
+    }
+
+    /// Gets or inserts a static string reference.
+    pub fn const_str(&mut self, s: impl AsRef<str>) -> (ConstHandle, StrRef) {
+        self.const_data_mut()
+            .const_str(s)
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct ConstData {
+    ints: HashMap<i64, (ConstHandle, IntRef)>,
+    strs: HashMap<String, (ConstHandle, StrRef)>,
+    const_pool: ConstPool,
+}
+
+impl ConstData {
+    /// Gets or inserts a static int reference.
+    pub fn const_int(&mut self, int: i64) -> (ConstHandle, IntRef) {
+        if let Some(pair) = self.ints.get(&int) {
+            pair.clone()
+        } else {
+            let obj = Int::new_obj(int);
+            let hdl = self.const_pool.push(obj.clone());
+            self.ints.insert(int, (hdl, obj.clone()));
+            (hdl, obj)
+        }
+    }
+
+    /// Gets or inserts a static string reference.
+    pub fn const_str(&mut self, s: impl AsRef<str>) -> (ConstHandle, StrRef) {
+        let s = s.as_ref();
+        if let Some(pair) = self.strs.get(s) {
+            pair.clone()
+        } else {
+            let obj = Str::new_obj(s.to_string());
+            let hdl = self.const_pool.push(obj.clone());
+            self.strs.insert(s.to_string(), (hdl, obj.clone()));
+            (hdl, obj)
+        }
+    }
+}