Debugger[gdb]: Dump QString and QByteArray of Qt 5.

Introduce functions to extract address and size of the
data from QString/QByteArray depending on the version
of Qt used.

Change-Id: I65a9c7ee05da7f8fe65f5916ccf699181782f8de
Reviewed-on: http://codereview.qt.nokia.com/1745


Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>