support DynamicAccess<T> to Dynamic<T> cast

std/haxe/DynamicAccess.hx

@@ -29,7 +29,7 @@ package haxe;
 
 	Basically, it wraps `Reflect` calls in a `Map`-like interface.
 **/
-abstract DynamicAccess<T>(Dynamic<T>) from Dynamic<T> {
+abstract DynamicAccess<T>(Dynamic<T>) from Dynamic<T> to Dynamic<T> {
 
 	/**
 		Creates a new structure.

tests/unit/src/unitstd/haxe/DynamicAccess.unit.hx

@@ -30,5 +30,9 @@ map.exists("bar") == false;
 map.exists("baz") == true;
 map.get("bar") == null;
 map["bar"] == null;
+
 map = {test: 2};
 map["test"] == 2;
+
+var d:Dynamic<Int> = map;
+d.test == 2;