Non-transferable symbols

[Nathan-Wall]

76 will have symbols copied by the mixin operator. This will be the default behavior for all symbols. However, we should probably add a way for symbols to be made non-transferable. Non-transferable symbols would not be copied by the mixin operator.

[Nathan-Wall]

Non-transferable symbol properties can now be defined on an object using the following pattern:

sym @foo;
var obj1 = { };
reflect.define(obj, @foo, {
    value: 'bar',
    writable: true,
    configurable: true,
    transferable: false
});
var obj2 = { @foo: 2 } := obj1;
obj1.@foo; // 1
obj2.@foo; // 2