Fold runtime/ crate into this source tree

While I like the idea of having a runtime completely decoupled from the
syntax and compiler, I don't think this is that big of a project for
that to be necessary or even useful yet.

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

src/vm/consts.rs

@@ -0,0 +1,47 @@
+use crate::obj::prelude::*;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct ConstHandle(usize);
+
+impl ConstHandle {
+    pub fn index(&self) -> usize {
+        self.0
+    }
+
+    pub fn new(handle: usize) -> Self {
+        ConstHandle(handle)
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct ConstPool {
+    pool: Vec<ObjRef>,
+}
+
+impl ConstPool {
+    pub fn new() -> Self {
+        Default::default()
+    }
+
+    pub fn push(&mut self, value: ObjRef) -> ConstHandle {
+        let hdl = ConstHandle::new(self.pool.len());
+        self.pool.push(value);
+        hdl
+    }
+
+    pub fn get(&self, hdl: ConstHandle) -> &ObjRef {
+        self.pool.get(hdl.index()).unwrap()
+    }
+
+    pub fn len(&self) -> usize {
+        self.pool.len()
+    }
+}
+
+impl std::ops::Index<ConstHandle> for ConstPool {
+    type Output = ObjRef;
+
+    fn index(&self, hdl: ConstHandle) -> &Self::Output {
+        self.get(hdl)
+    }
+}