Fix PrepareEmit error when evaluating delegates

The delegate class did not use the internal cache flag as other type definitions which caused the next evaluation to fail.

Before
![delegate_before](https://cloud.githubusercontent.com/assets/3028306/4603895/d240c6e4-517d-11e4-975b-6630ca7a513d.png)

After
![delegate](https://cloud.githubusercontent.com/assets/3028306/4603896/da6561f4-517d-11e4-9dc9-c24eae084adc.png)