Qt: implemented SM_SWSCROLLBARSPACING


git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@45115 4005530d-fff6-0310-9dd1-cebe43e6787f
Qt: removed workarounds for TScrollingWinControl after introducing SM_SWSCROLLBARSPACING.


git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@45116 4005530d-fff6-0310-9dd1-cebe43e6787f