command: allow using ASS tags on OSD messages

We don't allow this by default, because it would be silly if random
external data (like filenames or file tags) could accidentally trigger
them.

Add a property that magically disables this ASS tag escaping.

Note that malicious input could still disable ASS tag escaping by
itself. This would be annoying but harmless.

sub/osd_dummy.c

@@ -6,6 +6,9 @@
 #include "talloc.h"
 #include "osd.h"
 
+const char *osd_ass_0 = "";
+const char *osd_ass_1 = "";
+
 void osd_init_backend(struct osd_state *osd)
 {
 }