Add caching. (#134)

* Allow a module to have a different signature registry than the process-specific

* Add core ability to build compiled code caches

* Remove timing printouts

* Serialize/Deserialize memories to reduce copies

* Work more on api

* Relocate local functions relatively before external functions

* Fix incorrect definition in test

* merge errors caused by merge

* Fix emscripten compile

* Fix review comments

lib/runtime-core/src/export.rs

@@ -49,7 +49,7 @@ impl<'a> ExportIter<'a> {
     pub(crate) fn new(module: &'a ModuleInner, inner: &'a mut InstanceInner) -> Self {
         Self {
             inner,
-            iter: module.exports.iter(),
+            iter: module.info.exports.iter(),
             module,
         }
     }