[docs] Document more deprecated symbols

src/hb-deprecated.h

@@ -53,18 +53,29 @@ HB_BEGIN_DECLS
 #ifndef HB_DISABLE_DEPRECATED
 
 
+/**
+ * HB_SCRIPT_CANADIAN_ABORIGINAL:
+ *
+ * Use #HB_SCRIPT_CANADIAN_SYLLABICS instead:
+ *
+ * Deprecated: 0.9.20
+ */
 #define HB_SCRIPT_CANADIAN_ABORIGINAL		HB_SCRIPT_CANADIAN_SYLLABICS
 
 /**
  * HB_BUFFER_FLAGS_DEFAULT:
  *
  * Use #HB_BUFFER_FLAG_DEFAULT instead.
+ *
+ * Deprecated: 0.9.20
  */
 #define HB_BUFFER_FLAGS_DEFAULT			HB_BUFFER_FLAG_DEFAULT
 /**
  * HB_BUFFER_SERIALIZE_FLAGS_DEFAULT:
  *
- * Use HB_BUFFER_SERIALIZE_FLAG_DEFAULT instead.
+ * Use #HB_BUFFER_SERIALIZE_FLAG_DEFAULT instead.
+ *
+ * Deprecated: 0.9.20
  */
 #define HB_BUFFER_SERIALIZE_FLAGS_DEFAULT	HB_BUFFER_SERIALIZE_FLAG_DEFAULT
 

src/hb-graphite2.cc

@@ -195,6 +195,11 @@ _hb_graphite2_shaper_font_data_destroy (hb_graphite2_font_data_t *data HB_UNUSED
 #ifndef HB_DISABLE_DEPRECATED
 /**
  * hb_graphite2_font_get_gr_font:
+ * @font: An #hb_font_t
+ *
+ * Always returns %NULL. Use hb_graphite2_face_get_gr_face() instead.
+ *
+ * Return value: (nullable): Graphite2 font associated with @font.
  *
  * Since: 0.9.10
  * Deprecated: 1.4.2

src/hb-ot-deprecated.h

@@ -78,6 +78,8 @@ hb_ot_tag_from_language (hb_language_t language);
 /**
  * HB_OT_VAR_NO_AXIS_INDEX:
  *
+ * Do not use.
+ *
  * Since: 1.4.2
  * Deprecated: 2.2.0
  */