Fix UTF8 string serialization, allow UInt

hxd/net/Macros.hx

@@ -169,7 +169,7 @@ class Macros {
 			switch( a.toString() ) {
 			case "Float":
 				PFloat;
-			case "Int":
+			case "Int","UInt":
 				PInt;
 			case "Bool":
 				PBool;

hxd/net/Serializer.hx

@@ -330,8 +330,9 @@ class Serializer {
 		if( s == null )
 			addByte(0);
 		else {
-			addInt(s.length + 1);
-			out.addString(s);
+			var b = haxe.io.Bytes.ofString(s);
+			addInt(b.length + 1);
+			out.add(b);
 		}
 	}