feature #22758 Remove HHVM support (fabpot)

This PR was squashed before being merged into the 4.0-dev branch (closes #22758).

Discussion
----------

Remove HHVM support

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes-ish (for HHVM users)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

2125437c09 [WebServerBundle] removed obsolete ServerCommand abstract class
c7eeb32 removed HHVM support

Author: fabpot

Iterator/RecursiveDirectoryIterator.php

@@ -132,11 +132,6 @@ public function isRewindable()
             return $this->rewindable;
         }
 
-        // workaround for an HHVM bug, should be removed when https://github.com/facebook/hhvm/issues/7281 is fixed
-        if ('' === $this->getPath()) {
-            return $this->rewindable = false;
-        }
-
         if (false !== $stream = @opendir($this->getPath())) {
             $infos = stream_get_meta_data($stream);
             closedir($stream);