Remove duplicated code from QTestBasicStreamer.

Remove duplicated code from QTestBasicStreamer.

Instead of using the file output functions inherited from
QAbstractTestLogger, QTestLogger relied on QTestBasicStreamer having a
copy of these functions.  This commit removes the copied functions from
QTestBasicStreamer and makes it and QTestLogger use the original
functions from QAbstractTestLogger.

Change-Id: Icac1ae9d85cd39efd4c67c79104404dd56766b17
Reviewed-on: http://codereview.qt.nokia.com/3565
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>