Use platform specified duration for triggering MouseArea::onPressAndHold.

Task-number: QTBUG-24793
Change-Id: Ib663197eac46a17bfc73aaa945a6a2d52beb0b38
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Merge pull request #50 from mbrasser-jolla/master

Use platform specified duration for triggering MouseArea::onPressAndHold...