Code review feedback.

* Remove `Config::for_target` in favor of setter `Config::target`.
* Remove explicit setting of Cranelift flags in `Config::new` in favor of
  calling the `Config` methods that do the same thing.
* Serialize the package version independently of the data when serializing a
  module.
* Use struct deconstructing in module serialization to ensure tunables and
  features aren't missed.
* Move common log initialization in the CLI into `CommonOptions`.

tests/all/module_serialize.rs

@@ -11,6 +11,23 @@ fn deserialize_and_instantiate(store: &Store, buffer: &[u8]) -> Result<Instance>
     Ok(Instance::new(&store, &module, &[])?)
 }
 
+#[test]
+fn test_version_mismatch() -> Result<()> {
+    let engine = Engine::default();
+    let mut buffer = serialize(&engine, "(module)")?;
+    buffer[1] = 'x' as u8;
+
+    match Module::deserialize(&engine, &buffer) {
+        Ok(_) => bail!("expected deserialization to fail"),
+        Err(e) => assert_eq!(
+            e.to_string(),
+            "Module was compiled with incompatible Wasmtime version 'x.25.0'"
+        ),
+    }
+
+    Ok(())
+}
+
 #[test]
 fn test_module_serialize_simple() -> Result<()> {
     let buffer = serialize(