Reviewed by Sam Weinig.

* GNUmakefile.list.am: Removed ClipboardGtk.cpp.
* PlatformEfl.cmake: Removed ClipboardEfl.cpp.
* PlatformGTK.cmake: Removed ClipboardGtk.cpp.
* PlatformWinCE.cmake: Removed ClipboardWin.cpp.
* Target.pri: Removed ClipboardQt.cpp.
* WebCore.vcxproj/WebCore.vcxproj: Removed ClipboardWin.cpp and ClipboardWin.h.
* WebCore.vcxproj/WebCore.vcxproj.filters: Removed ClipboardWin.cpp and ClipboardWin.h.

* dom/Clipboard.cpp:
(WebCore::Clipboard::createDragImage): Added. Version that works for all platforms
other than Mac, identical to the old one used in GTK and Qt, and close to the one used
on Windows.

* platform/mac/ClipboardMac.mm: Trimmed includes down, and added a FIXME about next steps.

* platform/qt/DataTransferItemListQt.h: Removed "friend class ClipboardQt", which refers
to a now-nonexistent class.

* platform/efl/ClipboardEfl.cpp: Removed.
* platform/gtk/ClipboardGtk.cpp: Removed.
* platform/qt/ClipboardQt.cpp: Removed.
* platform/win/ClipboardWin.cpp: Removed.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154262 268f45cc-cd09-0410-ab3c-d52691b4dbfc