[set] Add a brute-force intersects(other_set)

src/hb-set.hh

@@ -120,6 +120,13 @@ struct hb_sparseset_t
   hb_sparseset_t& operator << (const hb_codepoint_pair_t& range)
   { add_range (range.first, range.second); return *this; }
 
+  bool intersects (const hb_set_t &other) const
+  {
+    hb_sparseset_t tmp = *this;
+    tmp.intersect (other);
+    return !tmp.is_empty ();
+  }
+
   bool intersects (hb_codepoint_t first, hb_codepoint_t last) const
   { return s.intersects (first, last); }