server: add prefix argument to red_printf_debug
server: add prefix argument to red_printf_debug

printed before function name. No central location for prefixes.
Adding "WORKER", "ASYNC", "MAIN" since those were the current users.

elmarco/spice-common,SPICE/spice-common,Fantu/spice-common,Fantu/spice-common,Fantu/spice-common,Fantu/spice-common,elmarco/spice-common,elmarco/spice-common,SPICE/spice-common,fgouget/spice-common,freedesktop-unofficial-mirror/spice__spice-common,elmarco/spice-common,fgouget/spice-common,freedesktop-unofficial-mirror/spice__spice-common,freedesktop-unofficial-mirror/spice__spice-common,fgouget/spice-common,SPICE/spice-common,fgouget/spice-common,freedesktop-unofficial-mirror/spice__spice-common