[type] Add HeadlessArray16Of

src/OT/Layout/GSUB/Ligature.hh

@@ -13,7 +13,7 @@ struct Ligature
   public:
   typename Types::HBGlyphID
 		ligGlyph;               /* GlyphID of ligature to substitute */
-  HeadlessArrayOf<typename Types::HBGlyphID>
+  HeadlessArray16Of<typename Types::HBGlyphID>
 		component;              /* Array of component GlyphIDs--start
                                          * with the second  component--ordered
                                          * in writing direction */

src/hb-open-type.hh

@@ -789,7 +789,7 @@ template <typename Type>
 using List16OfOffset16To = List16OfOffsetTo<Type, HBUINT16>;
 
 /* An array starting at second element. */
-template <typename Type, typename LenType=HBUINT16>
+template <typename Type, typename LenType>
 struct HeadlessArrayOf
 {
   static constexpr unsigned item_size = Type::static_size;
@@ -879,6 +879,7 @@ struct HeadlessArrayOf
   public:
   DEFINE_SIZE_ARRAY (sizeof (LenType), arrayZ);
 };
+template <typename Type> using HeadlessArray16Of = HeadlessArrayOf<Type, HBUINT16>;
 
 /* An array storing length-1. */
 template <typename Type, typename LenType=HBUINT16>

src/hb-ot-layout-gsubgpos.hh

@@ -3100,7 +3100,7 @@ struct ChainRule
 		backtrack;		/* Array of backtracking values
 					 * (to be matched before the input
 					 * sequence) */
-  HeadlessArrayOf<typename Types::HBUINT>
+  HeadlessArray16Of<typename Types::HBUINT>
 		inputX;			/* Array of input values (start with
 					 * second glyph) */
   Array16Of<typename Types::HBUINT>