If we have alpha in a 32bit rgb surface, ensure we send that
If we have alpha in a 32bit rgb surface, ensure we send that

If we don't then alpha is lost which is problematic if the surface
is later used as with alpha_blend and SRC_SURFACE_HAS_ALPHA.

alon/spice-server,dezelin/spice,fgouget/spice,Fantu/spice,elmarco/spice,SPICE/spice,alon/spice-server,SPICE/spice,elmarco/spice,ya-mouse/spice,ya-mouse/spice,freedesktop-unofficial-mirror/spice__spice,mathslinux/spice,SPICE/spice,fgouget/spice,fgouget/spice,mathslinux/spice,dezelin/spice,ya-mouse/spice,virtualAMP/spiceplay,mathslinux/spice,Fantu/spice,elmarco/spice,elmarco/spice,dezelin/spice,Fantu/spice,alon/spice-server,mathslinux/spice,alon/spice-server,dezelin/spice,freedesktop-unofficial-mirror/spice__spice,freedesktop-unofficial-mirror/spice__spice,virtualAMP/spiceplay,fgouget/spice,dezelin/spice,virtualAMP/spiceplay,virtualAMP/spiceplay,Fantu/spice,mathslinux/spice,elmarco/spice,freedesktop-unofficial-mirror/spice__spice,alon/spice-server,freedesktop-unofficial-mirror/spice__spice