[HB] Add buffer UTF-X API

src/hb-buffer.h

@@ -111,6 +111,27 @@ hb_buffer_add_glyph (hb_buffer_t    *buffer,
 		     hb_mask_t       mask,
 		     unsigned int    cluster);
 
+void
+hb_buffer_add_utf8 (hb_buffer_t  *buffer,
+		    const char   *text,
+		    unsigned int  text_len,
+		    unsigned int  item_offset,
+		    unsigned int  item_len);
+
+void
+hb_buffer_add_utf16 (hb_buffer_t    *buffer,
+		     const uint16_t *text,
+		     unsigned int    text_len,
+		     unsigned int    item_offset,
+		     unsigned int    item_len);
+
+void
+hb_buffer_add_utf32 (hb_buffer_t    *buffer,
+		     const uint32_t *text,
+		     unsigned int    text_len,
+		     unsigned int    item_offset,
+		     unsigned int    item_len);
+
 
 /* Getting glyphs out of the buffer */