Upstream iOS Clipboard and Pasteboard changes
<http://webkit.org/b/116062>

Reviewed by Darin Adler.

* WebCore.xcodeproj/project.pbxproj:
* dom/Clipboard.h:
* platform/Pasteboard.h:
* platform/ios/ClipboardIOS.h: Added.
* platform/ios/ClipboardIOS.mm: Added.
* platform/ios/PasteboardIOS.mm: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150049 268f45cc-cd09-0410-ab3c-d52691b4dbfc