Add methods to get screen coordinates of frames and views. Bug 268576,

accessible/src/atk/nsAccessibleText.cpp

content/svg/content/src/nsSVGSVGElement.cpp

layout/base/public/nsIFrame.h

layout/generic/nsFrame.cpp

layout/generic/nsIFrame.h

layout/html/base/src/nsFrame.cpp

layout/xul/base/src/nsBoxObject.cpp

layout/xul/base/src/nsBoxObject.h

layout/xul/base/src/nsMenuPopupFrame.cpp

layout/xul/base/src/nsMenuPopupFrame.h

view/public/nsIView.h

view/src/nsView.cpp