feature #26702 Mark ExceptionInterfaces throwable (ostrolucky)

This PR was merged into the 4.1-dev branch.

Discussion
----------

Mark ExceptionInterfaces throwable

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

This interface is meant to be catched, but currently it doesn't guarantee class extending it is an instance of Throwable or Exception.

Commits
-------

b2d8792908 Mark ExceptionInterfaces throwable

Author: fabpot

Exception/ExceptionInterface.php

@@ -16,6 +16,6 @@
  *
  * @author Bernhard Schussek <bschussek@gmail.com>
  */
-interface ExceptionInterface
+interface ExceptionInterface extends \Throwable
 {
 }