Add basic blocks and implementation of flattening thunks -> basic blocks

* Basic are a more linear way of representing code. Thunks beget basic
  blocks, which beget vectors of instructions.
* Basic blocks are also being flattened into a vector of instructions
  (hopefully, no tests done yet)
* OH yeah locals can be collected too (but currently are not being
  collected in the compiler, that should come soon)

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

src/vm/inst.rs

@@ -25,7 +25,7 @@ pub enum Inst {
     ///
     /// In code, it would look like this:
     ///
-    ///     target.symbol = source
+    /// `target.symbol = source`
     ///
     SetAttr(Sym),