Don't use the QRegExp methods that modify the object [QtWidgets]

Don't use the QRegExp methods that modify the object [QtWidgets]

QRegExp matching methods modify the object, which we don't want to. In
particular, when we receive a QRegExp from the user or we store in a
context that might require thread-safety, make sure we make a copy
before using it.

QRegularExpression has no such shortcoming.

Task-number: QTBUG-25064
Change-Id: I44cc44b75b3da10c5ece97cb6315c2c425327dc0
Reviewed-by: Alexis Menard <alexis.menard@openbossa.org>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>