[vtkusers] _cdecl* error in pickcells example

[Shaun Selha]

   When I try compiling the pickcells.cxx example I am getting an error
in the line:
    iren->SetEndPickMethod(PickCells, (void *)iren);
 that states
'SetEndPickMethod": cannot convert parameter 1 from 'void(void *)' to
'void(_cdecl*)(void *)'

Any suggestions on fixing this.

Shaun