display: use bitfields for surface flags
display: use bitfields for surface flags

Checking by value make the flag fields useless. Unfortunately, when
adding more flags, the server will have to ensure it can safely send it,
by checking some of new client caps (for some features).

Fantu/spice-gtk,elmarco/spice-gtk,SPICE/spice-gtk,SPICE/spice-gtk,SPICE/spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,guodong/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,guodong/spice-gtk,elmarco/spice-gtk,Fantu/spice-gtk,Fantu/spice-gtk,fgouget/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,guodong/spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,fgouget/spice-gtk,elmarco/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,elmarco/spice-gtk,flexVDI/spice-gtk