[docs] Fix comment syntax

To lower the number of gtk-doc warnings.

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