Begin internal reorganization.

This begins reorganizing how translation and compilation occur, and
setting up infrastructure for imports/exports and relocations. It
splits parts out of StandaloneRuntime, forming Module, Compilation,
and Instance structs, which can be used more independently.

It also simplifies the command-line interface, in a step towards
making simple tools that just expose the functionality of the
libraries.

lib/runtime/src/compilation.rs

@@ -0,0 +1,21 @@
+//! A `Compilation` contains the compiled function bodies for a WebAssembly
+//! module.
+
+use module::Module;
+
+/// An Instance of a WebAssemby module.
+#[derive(Debug)]
+pub struct Compilation<'module> {
+    /// The module this `Instance` is instantiated from.
+    pub module: &'module Module,
+
+    /// Compiled machine code for the function bodies.
+    pub functions: Vec<Vec<u8>>,
+}
+
+impl<'module> Compilation<'module> {
+    /// Allocates the runtime data structures with the given flags.
+    pub fn new(module: &'module Module, functions: Vec<Vec<u8>>) -> Self {
+        Self { module, functions }
+    }
+}