[set] Add copy constructor/assignment

src/hb-set.hh

@@ -40,10 +40,13 @@
 
 struct hb_set_t
 {
-  HB_DELETE_COPY_ASSIGN (hb_set_t);
   hb_set_t ()  { init (); }
   ~hb_set_t () { fini (); }
 
+  hb_set_t (const hb_set_t& other) : hb_set_t () { set (&other); }
+  void operator= (const hb_set_t& other) { set (&other); }
+  // TODO Add move construtor/assign
+
   struct page_map_t
   {
     int cmp (const page_map_t &o) const { return (int) o.major - (int) major; }