Wrong Class for new function GetLastSelected()

[StefanGrube]

VirtualTrees.pas could not be compiled anymore since the latest revision R1835(SVN). The class for the new function GetLastSelected() should be TBaseVirtualTree instead of TVirtualStringTree:

function TVirtualStringTree.GetLastSelected(ConsiderChildrenAbove: Boolean = False): PVirtualNode; -> function TBaseVirtualTree.GetLastSelected(ConsiderChildrenAbove: Boolean = False): PVirtualNode;