experimental GL video widget
temporary fix for text parameter ignoring expanded option
Don't use os.EX_OK in pg.exit()
ViewBox bugfixes:
  - drag rect now has large ZValue
  - fixed view linking with inverted y axis
ListParameter bugfix: allow unhashable types as parameter values.
added error message when GL shaders are not available
GLLinePLotItem accepts array of colors (thanks Felix!)
Allow QtProcess without local QApplication
documentation, bugfix
Support for FFT with non-uniform time sampling
Fixed parametertree selection bug
Python3 bugfixes
fixed PySide bug listing image formats
Corrected behavior of GraphicsView.setBackground
pg.plot() and pg.PlotWidget() now accept background argument
ImageExporter correctly handles QBrush with style=NoBrush
fixed TextParameter editor disappearing after focus lost