- drag rect now has large ZValue
  - fixed view linking with inverted y axis

temporary fix for text parameter ignoring expanded option
Don't use os.EX_OK in pg.exit()

  - Support for dynamic downsampling and view clipping in PlotDataItem / PlotItem
  - fixed __truediv__ handling
  - ViewBox updates to fix aspect locking (still broken)
  - AxisItem tries to be more clever about when to display tick text
  - Fix segmentation fault caused by exception inside GraphicsItem.paint()
  - Added 'x' scatter plot symbol
  - pg.mkPen supports dashes

This fixes memory leaks with PyQt 4.10 _except_ when using makeQImage(copy=False).
Tested on 4.9.3 and 4.10.2; need to be tested against other versions.

Minor edits

- fixed auto-levelling when normalization options change
- added autoHistogramRange argument to setImage

Configure matplotlib to use PySide in MatplotlibWidget

Fixed bugs in functions weave usage
Documented ROI signals
Fixed 3D view updating after every scene change