Add qtwebsockets as submodule

This just adds the module, it doesn't yet make it part of Qt 5.3
or anything like that

Change-Id: Icd42c4d2366e31298758a6ef82924bfb64a9f814
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>