Use setTimeZone if this method exists.

The php version is not a critical factor to choose the method, but we have to use setTimeZone, if it exists.
removed unneeded comment
Merge branch '2.2' into 2.3

* 2.2:
  [FrameworkBundle][Security] Replaced void return type with null for consistency
  fixed CS
  NativeSessionStorage regenerate
  removed unneeded comment
  Use setTimeZone if this method exists.
  Fix FileResource test
  fixed wrong usage of unset()
  [HttpFoundation] Fixed the way path to directory is trimmed.
  [Console] Fixed argument parsing when a single dash is passed.

Conflicts:
	src/Symfony/Component/HttpKernel/Debug/ErrorHandler.php