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: I252d1c47d7039caacec6aac5b572371d5b7efe32
Reviewed-by: Giuseppe D'Angelo <dangelog@gmail.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>