Reviewed by Darin Fisher.

        Turn all of the touch event handlers into RuntimeEnabledFeatures, and
        modify the createEvent methond on Document so that it won't create a
        TouchEvent if the feature is disabled.
        https://bugs.webkit.org/show_bug.cgi?id=37485

        * bindings/generic/RuntimeEnabledFeatures.cpp:
        * bindings/generic/RuntimeEnabledFeatures.h:
        (WebCore::RuntimeEnabledFeatures::touchEnabled):
        (WebCore::RuntimeEnabledFeatures::setTouchEnabled):
        (WebCore::RuntimeEnabledFeatures::ontouchstartEnabled):
        (WebCore::RuntimeEnabledFeatures::ontouchmoveEnabled):
        (WebCore::RuntimeEnabledFeatures::ontouchendEnabled):
        (WebCore::RuntimeEnabledFeatures::ontouchcancelEnabled):
        * dom/Document.cpp:
        (WebCore::Document::createEvent):
        * dom/Document.idl:
        * dom/Element.idl:
        * page/DOMWindow.idl:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@58363 268f45cc-cd09-0410-ab3c-d52691b4dbfc