[docs] Fix comment syntax

To lower the number of gtk-doc warnings.

src/hb-directwrite.cc

diff --git a/src/hb-directwrite.cc b/src/hb-directwrite.cc
index 5df1b2a..af0fd3d 100644
--- a/src/hb-directwrite.cc
+++ b/src/hb-directwrite.cc
@@ -659,7 +659,7 @@
     DWRITE_READING_DIRECTION_RIGHT_TO_LEFT :
     DWRITE_READING_DIRECTION_LEFT_TO_RIGHT;
 
-  /**
+  /*
   * There's an internal 16-bit limit on some things inside the analyzer,
   * but we never attempt to shape a word longer than 64K characters
   * in a single gfxShapedWord, so we cannot exceed that limit.
@@ -824,4 +824,4 @@
 
   /* Wow, done! */
   return true;
-}
\ No newline at end of file
+}

src/hb-ot-layout.cc

diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index 3049fa1..9fc88f6 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -458,6 +458,8 @@
 }
 
 /**
+ * hb_ot_layout_feature_get_lookups:
+ *
  * Since: 0.9.7
  **/
 unsigned int
@@ -475,6 +477,8 @@
 }
 
 /**
+ * hb_ot_layout_table_get_lookup_count:
+ *
  * Since: 0.9.22
  **/
 unsigned int
@@ -635,6 +639,8 @@
 }
 
 /**
+ * hb_ot_layout_collect_lookups:
+ *
  * Since: 0.9.8
  **/
 void
@@ -679,6 +685,8 @@
 }
 
 /**
+ * hb_ot_layout_lookup_collect_glyphs:
+ *
  * Since: 0.9.7
  **/
 void
@@ -727,6 +735,8 @@
 }
 
 /**
+ * hb_ot_layout_lookup_would_substitute:
+ *
  * Since: 0.9.7
  **/
 hb_bool_t
@@ -768,6 +778,8 @@
 }
 
 /**
+ * hb_ot_layout_lookup_substitute_closure:
+ *
  * Since: 0.9.7
  **/
 void
@@ -805,6 +817,8 @@
 }
 
 /**
+ * hb_ot_layout_get_size_params:
+ *
  * Since: 0.9.10
  **/
 hb_bool_t

src/hb-unicode.h

diff --git a/src/hb-unicode.h b/src/hb-unicode.h
index 33b68aa..6a15cb0 100644
--- a/src/hb-unicode.h
+++ b/src/hb-unicode.h
@@ -405,6 +405,8 @@
 /* accessors */
 
 /**
+ * hb_unicode_combining_class:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN hb_unicode_combining_class_t
@@ -412,6 +414,8 @@
 			    hb_codepoint_t unicode);
 
 /**
+ * hb_unicode_eastasian_width:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN unsigned int
@@ -419,6 +423,8 @@
 			    hb_codepoint_t unicode);
 
 /**
+ * hb_unicode_general_category:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN hb_unicode_general_category_t
@@ -426,6 +432,8 @@
 			     hb_codepoint_t unicode);
 
 /**
+ * hb_unicode_mirroring:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN hb_codepoint_t
@@ -433,6 +441,8 @@
 		      hb_codepoint_t unicode);
 
 /**
+ * hb_unicode_script:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN hb_script_t
@@ -440,6 +450,8 @@
 		   hb_codepoint_t unicode);
 
 /**
+ * hb_unicode_compose:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN hb_bool_t
@@ -449,6 +461,8 @@
 		    hb_codepoint_t     *ab);
 
 /**
+ * hb_unicode_decompose:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN hb_bool_t
@@ -458,6 +472,8 @@
 		      hb_codepoint_t     *b);
 
 /**
+ * hb_unicode_decompose_compatibility:
+ *
  * Since: 0.9.2
  **/
 HB_EXTERN unsigned int