Reviewed by Adam.

        Implementation of actions for the new context menus.

        * WebCore.exp:
        * WebCore.xcodeproj/project.pbxproj:
        * bridge/EditorClient.h: Declaration of shouldInsertText.
        * bridge/mac/FrameMac.h: Two new spelling functions.
        * bridge/mac/FrameMac.mm:
        (WebCore::FrameMac::ignoreSpelling):
        (WebCore::FrameMac::learnSpelling):
        * editing/Editor.cpp:
        (WebCore::Editor::shouldInsertText): Call into the client.
        * editing/Editor.h:
        * editing/EditorInsertAction.h: Added.
        (WebCore::): The WebCore equivalent of WebViewInsertAction. This is 
        defined in its own header so that we can use it from Editor.h and 
        EditorClient.h without having one of the above include the other.
        * page/ContextMenuClient.h: A few currently WebKit-implemented 
        function needed for menu actions.
        * page/ContextMenuController.cpp:
        (WebCore::makeGoogleSearchURL):
        (We...