Replace all remaining functions deprecated in Qt 5, if possible.

These are:
    - QInputDialog::getInteger() [-> getInt()]
    - QKeySequence::operator QString() [-> toString()]
    - QRegion::intersect() [-> intersected()]
    - qVariantCanConvert() [-> QVariant::canConvert()]

Plus some left-over occurrences of qFindChild() and
QAbstractItemModel::reset() that were missed by the
respective earlier patches.

All deprecated features still left are not trivially
replaceable, i.e. the code using them cannot be made
to compile with both Qt 4 and Qt 5.

Change-Id: I32541681bbf66b0fef78f5c7025521f9ff84f463
Reviewed-by: hjk <qthjk@ovi.com>