Minor. Add documentation.

include/freetype/ftglyph.h

@@ -257,6 +257,8 @@ FT_BEGIN_HEADER
    *     The index of the glyph to be rendered. I think it's necessary
    *     because one document can contain multiple glyphs.
    *
+   *   metrics ::
+   *     A metrics object storing the size information.
    */
   typedef struct  FT_SvgGlyphRec_
   {

include/freetype/svgrenderer.h

@@ -162,6 +162,9 @@ FT_BEGIN_HEADER
    *
    *   svg_document_length ::
    *     The length of the SVG document string.
+   *
+   *   metrics ::
+   *     A metrics object storing the size information.
    */
 
   typedef struct FT_SVG_DocumentRec_