The so-called "Vista/7 helpers" only define interfaces missing from mingw*

Remove duplicate declarations already in all mingw headers, include the
correct headers instead.

Link video outputs against libuuid to get the existing UUID instead of
defining our own.

Define the C interfaces as Microsoft does it by using lpVtbl for the
virtual table pointer.
See http://blogs.msdn.com/b/oldnewthing/archive/2004/02/05/68017.aspx

Define a C++ interface to TaskbarList3 for qt4, keep the C for video outputs.
Define only a C++ interface to IApplicationAssociationRegistrationUI

Define TaskbarList3->SetTabActive() correctly.
See http://msdn.microsoft.com/en-us/library/windows/desktop/dd391699(v=vs.85).aspx

ifdef the TaskbarList3 interface because mingw-w64 defines it already.