Disconnects Store state fields from Compiler (#1761)

*  Moves CodeMemory, VMInterrupts and SignatureRegistry from Compiler
*  CompiledModule holds CodeMemory and GdbJitImageRegistration
*  Store keeps track of its JIT code
*  Makes "jit_int.rs" stuff Send+Sync
*  Adds the threads example.

tests/all/instance.rs

@@ -4,10 +4,10 @@ use wasmtime::*;
 #[test]
 fn wrong_import_numbers() -> Result<()> {
     let store = Store::default();
-    let module = Module::new(&store, r#"(module (import "" "" (func)))"#)?;
+    let module = Module::new(store.engine(), r#"(module (import "" "" (func)))"#)?;
 
-    assert!(Instance::new(&module, &[]).is_err());
+    assert!(Instance::new(&store, &module, &[]).is_err());
     let func = Func::wrap(&store, || {});
-    assert!(Instance::new(&module, &[func.clone().into(), func.into()]).is_err());
+    assert!(Instance::new(&store, &module, &[func.clone().into(), func.into()]).is_err());
     Ok(())
 }