libobs: Add video_reset signal

Signals when a video reset has completed. This is mainly useful when
canvases or views are used, whose mixes will have been freed or
recreated during the reset.

libobs/obs.c

@@ -695,6 +695,9 @@ static int obs_init_video(struct obs_video_info *ovi)
 
 	video->thread_initialized = true;
 
+	calldata_t parameters = {0};
+	signal_handler_signal(obs->signals, "video_reset", &parameters);
+
 	return OBS_VIDEO_SUCCESS;
 }
 
@@ -1053,6 +1056,8 @@ static const char *obs_signals[] = {
 	"void hotkey_unregister(ptr hotkey)",
 	"void hotkey_bindings_changed(ptr hotkey)",
 
+	"void video_reset()",
+
 	NULL,
 };