[Stable] merge:qwt-5.0.2

[ertugrulerata]

version bump 
7 bug fixed

1. QwtPlotCurve::Xfy curve type fixed
2. Memory leak in QwtLegend fixed
3. Vertical alignment of rich texts fixed
4. Workaround for a Qt4 bug added, that produces horrible performance
   when painting curves with a pen width > 1.
5. Background for the tracker text of QwtPickers fixed.
   Improved (faster + better rendered texts) implementation of
   painting tracker texts, using capabilities of Qt >= 4.3.
6. QwtArrowButton/QwtCounter: workaround for layout bug ( Qt < 4.3 )
   of the Cleanlook style added.
7. A couple of minor fixes