libobs: Add the ability to make sources obsolete

This allows the ability to do things such as change defaults or
properties of sources without necessarily breaking older user
configurations that had older defaults or properties.

libobs/obs-source.h

@@ -156,6 +156,11 @@ enum obs_icon_type {
  */
 #define OBS_SOURCE_CAP_DISABLED (1 << 10)
 
+/**
+ * Source type is obsolete (has been updated with new defaults/properties/etc)
+ */
+#define OBS_SOURCE_CAP_OBSOLETE OBS_SOURCE_CAP_DISABLED
+
 /**
  * Source should enable monitoring by default.  Monitoring should be set by the
  * frontend if this flag is set.