about commit 83ea19670eff0febff516380fb59a65a1d7667a9: use Qt::Popup in tasks applet

[Jacopo De Simoi]

Hi plasma ppl,

The issue with pixmap initialization I referred to in my previous thread hits most notably popups in the tasks applet. Even if good care has been put in avoiding this to happen (with the fix described in the previous thread), the commit in 
the subject breaks this attempts, since, for some reason, the Qt pixmap creation strategy is the same for windows with 
Qt::Popup or with Qt::WA_NoSystemBackground. 
That is, even it WA_NoSystemBackground is unset, but Qt::Popup is set, then the Sliding Popup effect will break. 

This strategy is quite debatable, but apparently has been there forever (<4.5) 
Can we workaround this fact? reverting this commit should do it, is it worth it?
Any other solutions? the glitch is quite horrible (at least on my machine)

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As a side note, this commit introduces a regression: when a popup is opened, clicking 
on another task item makes the popup retract, but somehow focus is still kept by the
same task item; clicking anywhere in the tasks applet (but on the appropriate task item) makes the popup
open and retract until one clicks on the appropriate task item is clicked again. 
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Thanks