KWindow: add SetActiveWindow() member function
all: use const if possible
KDialog: return directly the value from WinLoadDlg()
KWindow: add GetParent() and GetOwner() utility member functions
KWindow: add Resize() utility member function
KWindow: change the return type of Centering() to bool
KWindow: remove useless virtual
KFileDlg: return directly the value from WinFileDlg()
KWindow: move _mapHWND and _hwnd to private section
all: move member variables and functions to private section