package/cups-filters: fix broken symlink in installation

package/cups-filters: fix broken symlink in installation

The patch used previously to support versions of ln lacking the '-r'
option generated broken links:

    $ file target/usr/lib/cups/backend/driverless
    target/usr/lib/cups/backend/driverless: broken symbolic link to ../../usr/lib/cups/driver/driverless

Add a squashing of two patches already applied upstream that provide a
better solution:

    https://github.com/OpenPrinting/cups-filters/pull/154
    https://github.com/OpenPrinting/cups-filters/pull/157

Signed-off-by: Carlos Santos <unixmania@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>