Completely revert the thing back

src/hb-open-type.hh

diff --git a/src/hb-open-type.hh b/src/hb-open-type.hh
index 1471f51..57b22a8 100644
--- a/src/hb-open-type.hh
+++ b/src/hb-open-type.hh
@@ -279,15 +279,6 @@
     return StructAtOffset<Type> (base, *this);
   }
 
-  template <typename Base>
-  friend const Type& operator + (const Base &base, const OffsetTo &offset) { return offset (base); }
-  template <typename Base>
-  friend const Type& operator + (const OffsetTo &offset, const Base &base) { return offset (base); }
-  template <typename Base>
-  friend Type& operator + (Base &base, OffsetTo &offset) { return offset (base); }
-  template <typename Base>
-  friend Type& operator + (OffsetTo &offset, Base &base) { return offset (base); }
-
   Type& serialize (hb_serialize_context_t *c, const void *base)
   {
     return * (Type *) Offset<OffsetType>::serialize (c, base);
@@ -366,6 +357,11 @@
 template <typename Type>
 using LNNOffsetTo = LOffsetTo<Type, false>;
 
+template <typename Base, typename OffsetType, bool has_null, typename Type>
+static inline const Type& operator + (const Base &base, const OffsetTo<Type, OffsetType, has_null> &offset) { return offset (base); }
+template <typename Base, typename OffsetType, bool has_null, typename Type>
+static inline Type& operator + (Base &base, OffsetTo<Type, OffsetType, has_null> &offset) { return offset (base); }
+
 
 /*
  * Array Types