D3D: Reintroduce depencency on D3DX11 because it's the most straightforward way to bring back some broken features. The Dolphin development team is incapable of providing sufficient replacement for its previous usage in Dolphin and the advantages of dropping the dependency do not justify the removal of screenshots and texture dumping. From now on, d3dx11.h, d3dx11async.h, d3dx11core.h and d3dx11tex.h are required to be stored somewhere in the header include path. I don't know if this is the case for anyone else than me, but I can't really say that I care after having people randomly merge unfinished branches into master.