Verify code generation for the new never type

[Ocramius]

The test suite includes scenarios that handle the : void return type of methods:

• ProxyManager/tests/ProxyManagerTestAsset/VoidCounter.php

  Lines 7 to 17 in 95f9ccf

  	class VoidCounter
  	{
  	/**
  	* @var int
  	*/
  	public $counter = 0;
  	public function increment(int $amount) : void
  	{
  	$this->counter += $amount;
  	}

• https://github.com/Ocramius/ProxyManager/blob/95f9ccf6711b91736ce6da261c24252b84a290c7/tests/ProxyManagerTestAsset/VoidMethodTypeHintedClass.php
• https://github.com/Ocramius/ProxyManager/blob/95f9ccf6711b91736ce6da261c24252b84a290c7/tests/ProxyManagerTestAsset/VoidMethodTypeHintedInterface.php

We need:

1. similar classes, but using the never type ( https://wiki.php.net/rfc/noreturn_type )
2. make sure we find usages of above classes, and introduce tests around the never type wherever they are used (using the newly introduced assets)

[Ocramius]

Note: this may be an absolute beast to handle, because we need to get rid of most generated return; statements from proxies.