[Docs] Add gtk-doc comments to hb-coretext.

src/hb-coretext.cc

diff --git a/src/hb-coretext.cc b/src/hb-coretext.cc
index 66f0fce..8e46e1a 100644
--- a/src/hb-coretext.cc
+++ b/src/hb-coretext.cc
@@ -293,13 +293,32 @@
   CFRelease ((CGFontRef) data);
 }
 
+/**
+ * hb_coretext_face_create:
+ * @cg_font: The CGFontRef to work upon
+ *
+ * Creates an #hb_face_t face object from the specified
+ * CGFontRef.
+ *
+ * Return value: the new #hb_face_t face object
+ *
+ * Since: 0.9.10
+ */
 hb_face_t *
 hb_coretext_face_create (CGFontRef cg_font)
 {
   return hb_face_create_for_tables (reference_table, CGFontRetain (cg_font), _hb_cg_font_release);
 }
 
-/*
+/**
+ * hb_coretext_face_get_cg_font:
+ * @face: The #hb_face_t to work upon
+ *
+ * Fetches the CGFontRef associated with an #hb_face_t
+ * face object
+ *
+ * Return value: the CGFontRef found
+ *
  * Since: 0.9.10
  */
 CGFontRef
@@ -365,10 +384,17 @@
   return font->data.coretext;
 }
 
-
-/*
+/**
+ * hb_coretext_font_create:
+ * @ct_font: The CTFontRef to work upon
+ *
+ * Creates an #hb_font_t font object from the specified
+ * CTFontRef.
+ *
+ * Return value: the new #hb_font_t font object
+ *
  * Since: 1.7.2
- */
+ **/
 hb_font_t *
 hb_coretext_font_create (CTFontRef ct_font)
 {
@@ -389,6 +415,17 @@
   return font;
 }
 
+/**
+ * hb_coretext_face_get_ct_font:
+ * @font: #hb_font_t to work upon
+ *
+ * Fetches the CTFontRef associated with the specified
+ * #hb_font_t font object.
+ *
+ * Return value: the CTFontRef found
+ *
+ * Since: 0.9.10
+ */
 CTFontRef
 hb_coretext_font_get_ct_font (hb_font_t *font)
 {

src/hb-coretext.h

diff --git a/src/hb-coretext.h b/src/hb-coretext.h
index 4b0a6f0..e53dbaf 100644
--- a/src/hb-coretext.h
+++ b/src/hb-coretext.h
@@ -40,8 +40,40 @@
 HB_BEGIN_DECLS
 
 
+/**
+ * HB_CORETEXT_TAG_MORT:
+ *
+ * The #hb_tag_t tag for the `mort` (glyph metamorphosis) table,
+ * which holds AAT features. 
+ *
+ * For more information, see 
+ * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6mort.html
+ *
+ **/
 #define HB_CORETEXT_TAG_MORT HB_TAG('m','o','r','t')
+
+/**
+ * HB_CORETEXT_TAG_MORX:
+ *
+ * The #hb_tag_t tag for the `morx` (extended glyph metamorphosis)
+ * table, which holds AAT features. 
+ *
+ * For more information, see
+ * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6morx.html
+ *
+ **/
 #define HB_CORETEXT_TAG_MORX HB_TAG('m','o','r','x')
+
+/**
+ * HB_CORETEXT_TAG_KERX:
+ *
+ * The #hb_tag_t tag for the `kerx` (extended kerning) table, which
+ * holds AAT kerning information. 
+ *
+ * For more information, see 
+ * https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6kerx.html
+ *
+ **/
 #define HB_CORETEXT_TAG_KERX HB_TAG('k','e','r','x')