Fix issue #124
Fix issue #124

Fix parsing multiline strings.

less.php fails to compile strings with escaped newlines, e.g.:
    content: 'This is a \
    multiline string.';
This includes `backslash + newline` to the string regex matching.

iisisrael/less.php,iisisrael/less.php,atdt/less.php,TomArrow/less.php,TomArrow/less.php,atdt/less.php,atdt/less.php,iisisrael/less.php,oyejorge/less.php,oyejorge/less.php,TomArrow/less.php,oyejorge/less.php