[Patch] System Settings : Improve General/Advanced tabs visibility

[Michael Lentner]

It would be better to use a tab widget with a custom bar. Using a tab bar 
without a tab frame should be avoided because the tab lines need a adjacent 
frame with the same line style. You see it in your screenshot, it doesn't fit 
and looks broken. Some styles may draw their tab background on the tab widget 
and only separators on the tabs. This will break also.
And please make sure that the tabs fill the entire bar. With an uneven bar 
width the tabs will leave a gap of one pixel, which will make them jerky if 
the window gets resized.

Michael