drop any fallback code related to curl - refs https://github.com/owncloud/core/pull/14838#issuecomment-78586447

This reverts commit 6a1a4880.

The file:// protocol does not work with curl when an open_basedir is set.

This fixes https://github.com/owncloud/core/issues/12016

Fixes https://github.com/owncloud/core/pull/11501#issuecomment-58794405

Otherwise it would fall into the 'win' else block because strpos($os, 'win') does also match 'darwin' what is the `php_uname` for OS X.

Large file helper use cURL to determine file sizes. Thus filenames must be
urlencoded in case special symbols like '#' can cause BadRequest errors.

Signed-off-by: Tony Zelenoff <antonz@parallels.com>

Determining the file size using the exec() method is implemented for Linux, BSD, and Windows. However, on systems matching neither platform name (like SunOS), the fall-through path will return a file size result constituting a zero size instead of an invalid null return value.