Support plain QNX in mm-renderer mediaplayer impl

On plain QNX, the native events are plain screen_event_t's,
instead of being wrapped in bps_event_t.

The bps/mm-renderer interface isn't available on QNX, thus
those parts are replaced by reading directly from mm-renderer's
PPS objects.

Change-Id: I38772ddad04432ff099455a730ce0034f07db70d
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>