directfb-examples: bump to version 1.6.0

The previous version 1.2.0 isn't acting well with directfb 1.6.3 so
increasing the version to the latest available version on directfb.org.

Signed-off-by: Carsten Schoenert <c.schoenert@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>