Make it compile and link again. (Qt) Includes implementation of a few stubs

Make it compile and link again. (Qt)  Includes implementation of a few stubs
which should be moved to other locations, as well as a non-Qt-specific change
to make it compile (nil->ResourceResponse()).  Qt port continues to function as
well as before.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@18650 268f45cc-cd09-0410-ab3c-d52691b4dbfc