Normalize $url and $current_path/$_GET[q'] when detecting redirect loops in context_redirect_validate_redirect()

Currently we compare the destination url against $_GET['q'] and against drupal_get_path_alias($_GET['q']).

If the destination url is not an internal path, but an absolute url to an internal page then this check won't detect the loop.

If we use drupal_get_normal_path() on both $url and $current_path, then convert both normalized paths to absolute urls with url() then compare the two results we should have a more robust way to detect redirect loops in a single if() statement.