Don't use the QRegExp methods that modify the object

Don't use the QRegExp methods that modify the object

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: I2c4d5f4b60d6b3569568103cd7107cd2adaa3ae8
Reviewed-by: Giuseppe D'Angelo <dangelog@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>