[Console] Make sure formatter is the same

The parent constructor will create a new formatter if the $formatter parameter is null
This fix avoids that the formatter becomes 2 different instances in $this and $this->stderr
added XSD to PHPUnit configuration
Merge branch '2.3' into 2.4

* 2.3:
  bumped Symfony version to 2.3.18
  updated VERSION for 2.3.17
  update CONTRIBUTORS for 2.3.17
  updated CHANGELOG for 2.3.17
  added XSD to PHPUnit configuration
  bug #11319 [HttpKernel] Ensure the storage exists before purging it in ProfilerTest
  [Translation] Added unescaping of ids in PoFileLoader
  updated italian translation for validation messages
  [DomCrawler] Fix docblocks and formatting.
  [DomCrawler] Remove the query string and the anchor of the uri of a link
  Simplified the Travis test command
  [Console] Make sure formatter is the same

Conflicts:
	src/Symfony/Component/HttpKernel/Kernel.php