QStyle - tooltip - add wakeDelay and sleepDelay as styleHints

In earlier patches we allowed the user to control the
tooltip duration. However the user still couldn't control
the wake delay and sleep delay.

This patch changes that and is the final patch in solving:

Task-number: QTBUG-1016

Change-Id: I5e2c719737634ad7f371ad03691744612472ae70
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>