Remove no-longer-used PopUpButton.

        * WebCore.vcproj/WebCore/WebCore.vcproj: Remove PopUpButton.h
        * WebCore.xcodeproj/project.pbxproj: Remove PopUpButton.h,
	PopUpButtonMac.mm
        * platform/PopUpButton.h: Removed.
        * platform/mac/PopUpButtonMac.mm: Removed.
        * platform/win/TemporaryLinkStubs.cpp: Remove PopUpButton:: methods
        * rendering/DeprecatedRenderSelect.cpp: Change #include of
	PopUpButton.h to ListBox.h



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@16624 268f45cc-cd09-0410-ab3c-d52691b4dbfc