Disabled D-Bus support for WinCE

We're currently working on porting DBus to Windows Mobile 6 and have it mostly working, pending inclusion in the master dbus repo on freedesktop.org.
However currently Qt doesn't support building the QtDBus module for winCE, even when passing the -dbus-linked option to configure.exe. It seems to be a historical thing (no support for dbus on winCE in the past), as it builds just fine when forcing the module to build.

Attached is a patch to enable the dbus module on winCE again. It includes :

• enabling QtDBus in the top-level .pro file if the option is specified through configure.exe
• adjusting libraries for winCE in dbus.pro
• a simple build fix for qdbusxml2cpp.cpp, which includes headers not available with the Windows Mobile 6 SDK, but these headers aren't needed anyway they just seem like leftovers from old code not there anymore (tested with a normal win32 build too)