Error in check for incompatible types in super interfaces

When a generic interface (Using a template type) extends two other generic interfaces containing the same compatible methods then the closure compiler (v20150126) complains about incompatible types. Here is a short example:

``` js
/**
* @template T
* @interface
* @extends B.
* @extends C.
*/
function A() {}

/**
* @template T
* @interface
*/
function B() {}

/** @return {T} */
B.prototype.getValue = function() {};

/**
* @template T
* @interface
*/
function C() {}

/** @return {T} */
C.prototype.getValue = function() {};
```

And here is the compiler output:

```
$ jscc test.js -W VERBOSE
test.js:7: WARNING - Interface A has a property getValue with incompatible types in its super interfaces B and C
function A() {}
^

0 error(s), 1 warning(s), 100.0% typed
```

The check works correctly with the new type inference but because of other problems with the new type inference I'm currently still using the default type inference so I hope this bug could be fixed there, too.