Description:
------------
A new feature added in 5.6 allows functions to be imported and aliased.
It is possible to re-alias an already imported function but that does not seem to work.

Test script:
---------------
<?php

namespace foo\bar {
  function baz() { return __FUNCTION__; }
}

namespace {
  use function foo\bar\baz as foobarbaz;
  use function foobarbaz as foobar;

  var_dump(foobar());
}

Expected result:
----------------
string(11) "foo\bar\baz"
string(11) "foo\bar\baz"

Actual result:
--------------
string(11) "foo\bar\baz"

Fatal error: Call to undefined function foobarbaz() in %s/test_case.php on line 12