Correct return types for numerous D3D9 interface methods.
Correct return types for numerous D3D9 interface methods.

Many methods including IUnknown::AddRef/Release were returning
`*mut IDirect3D...` pointers. Method arguments formatted to be one per line.

docbrown/winapi-rs,ROki1988/winapi-rs,Osspial/winapi-rs,alexcrichton/winapi-rs,roblabla/winapi-rs,gentoo90/winapi-rs,bungcip/winapi-rs,tomaka/winapi-rs,DenisKolodin/winapi-rs,Connorcpu/winapi-rs,overdrivenpotato/winapi-rs,DoumanAsh/winapi-rs,bvinc83/winapi-rs,jmesmon/winapi-rs,Boddlnagg/winapi-rs