Description:
------------
Attempting to access extensionless ZIP archives using the `phar://` wrapper results in errors.

Examples (assumes the file being read is an arbitrary ZIP archive containing one or more files):

This:
```
%PATH%>php.exe -r "$foo=scandir('phar://x:/xxx.xxx');var_dump($foo);
```

..generates an array whereby elements represent the files contained by the archive (expected).

Whereas this:
```
%PATH%>php.exe -r "$foo=scandir('phar://x:/xxx');var_dump($foo);
```

..generates this (not expected):
```
PHP Warning:  scandir(phar://x:/xxx): failed to open dir: phar error: no directory in "phar://x:/xxx", must have at least phar://x:/xxx/ for root directory (always use full path to a new phar)
phar url "phar://x:/xxx" is unknown in Command line code on line 1
PHP Warning:  scandir(): (errno 9): Bad file descriptor in Command line code on line 1
bool(false)
```

Bug discovered via: https://github.com/phpMussel/phpMussel/issues/155

Reproduced against latest releases on all currently supported branches (5.6, 7.0, 7.1, 7.2). Not tested against any older versions or unsupported branches.