Use a custom progress bar UI on mac to see the green / red status colours.
Reduce custom progress bar to simply setting the ui to BasicProgressBarUI.

The intention was not really to set the indeterminate progress bar to
this oval thingy, only to be able to have the widget pick up color changes.
Merge pull request #32 from marcpa00/mac-custom-probressbar-ui

Use a custom progress bar UI on mac to see the green / red status colours