Fix QGeoCoordinate::toString() when rounding long/lat corner cases

Change-Id: I14da28acbd124e07da42fbf5efc3a501267f86f3
Task-number: QTBUG-41739
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Merge remote-tracking branch 'origin/5.4' into dev

Change-Id: I7eb1d75a392e5872e5565bec2c5f7fcddbc32e78