NOTE: test_form_upload() is broken. Uploading files via Symfony fails to
retain $_FILES['fileupload']['type'] even if it set explicitely. This appears
to be a bug in Symfony. Since the current version of filespec::is_image()
relies on the mimetype, these tests will __fail__. filespec::is_image() has
been fixed in https://github.com/phpbb/phpbb3/pull/833 however.
PHPBB3-10941
