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/instance.rs

@@ -0,0 +1,90 @@
+//! An `Instance` contains all the runtime state used by execution of a wasm
+//! module.
+
+use cretonne::ir;
+use cton_wasm::GlobalIndex;
+use module::Module;
+
+const PAGE_SIZE: usize = 65536;
+
+/// An Instance of a WebAssemby module.
+#[derive(Debug)]
+pub struct Instance {
+    /// WebAssembly table data.
+    pub tables: Vec<Vec<usize>>,
+
+    /// WebAssembly linear memory data.
+    pub memories: Vec<Vec<u8>>,
+
+    /// WebAssembly global variable data.
+    pub globals: Vec<u8>,
+}
+
+impl Instance {
+    /// Create a new `Instance`.
+    pub fn new(module: &Module) -> Self {
+        let mut result = Self {
+            tables: Vec::new(),
+            memories: Vec::new(),
+            globals: Vec::new(),
+        };
+        result.instantiate_tables(module);
+        result.instantiate_memories(module);
+        result.instantiate_globals(module);
+        result
+    }
+
+    /// Allocate memory in `self` for just the tables of the current module,
+    /// without any initializers applied yet.
+    fn instantiate_tables(&mut self, module: &Module) {
+        debug_assert!(self.tables.is_empty());
+        self.tables.reserve(module.tables.len());
+        for table in &module.tables {
+            let len = table.size;
+            let mut v = Vec::with_capacity(len);
+            v.resize(len, 0);
+            self.tables.push(v);
+        }
+    }
+
+    /// Allocate memory in `instance` for just the memories of the current module,
+    /// without any initializers applied yet.
+    fn instantiate_memories(&mut self, module: &Module) {
+        debug_assert!(self.memories.is_empty());
+        // Allocate the underlying memory and initialize it to all zeros.
+        self.memories.reserve(module.memories.len());
+        for memory in &module.memories {
+            let len = memory.pages_count * PAGE_SIZE;
+            let mut v = Vec::with_capacity(len);
+            v.resize(len, 0);
+            self.memories.push(v);
+        }
+    }
+
+    /// Allocate memory in `instance` for just the globals of the current module,
+    /// without any initializers applied yet.
+    fn instantiate_globals(&mut self, module: &Module) {
+        debug_assert!(self.globals.is_empty());
+        // Allocate the underlying memory and initialize it to all zeros.
+        let globals_data_size = module.globals.len() * 8;
+        self.globals.resize(globals_data_size, 0);
+    }
+
+    /// Returns a slice of the contents of allocated linear memory.
+    pub fn inspect_memory(&self, memory_index: usize, address: usize, len: usize) -> &[u8] {
+        &self.memories.get(memory_index).expect(
+            format!(
+                "no memory for index {}",
+                memory_index
+            ).as_str(),
+        )
+            [address..address + len]
+    }
+
+    /// Shows the value of a global variable.
+    pub fn inspect_global(&self, global_index: GlobalIndex, ty: ir::Type) -> &[u8] {
+        let offset = global_index * 8;
+        let len = ty.bytes() as usize;
+        &self.globals[offset..offset + len]
+    }
+}