initial qmake build system

This is an early work in progress set of project files for building audacious with qmake.  Absolutely no effort at this time is made towards supporting Gtk+ builds with these.

I think that the Qt builds should use qmake and the Gtk+ ones should use autotools.  Then we just delete the old autoconf based system after 3.6 is released, but this will allow developers to at least get used to working with qmake for their plugins in the plugins tree.

A similar infrastructure will appear for audacious-plugins soon.