Minor, replace hb_set_add with private API
diff --git a/src/hb-ot-map.cc b/src/hb-ot-map.cc
index d40c67a..e4bb4b6 100644
--- a/src/hb-ot-map.cc
+++ b/src/hb-ot-map.cc
@@ -38,7 +38,7 @@
 void hb_ot_map_t::collect_lookups (unsigned int table_index, hb_set_t *lookups_out) const
 {
   for (unsigned int i = 0; i < lookups[table_index].length; i++)
-    hb_set_add (lookups_out, lookups[table_index][i].index);
+    lookups_out->add (lookups[table_index][i].index);
 }
 
 
diff --git a/src/hb-subset-cff-common.hh b/src/hb-subset-cff-common.hh
index 7388f4f..3c66119 100644
--- a/src/hb-subset-cff-common.hh
+++ b/src/hb-subset-cff-common.hh
@@ -916,7 +916,7 @@
 				  hb_set_t *closure,
 				  const subr_subset_param_t &param)
   {
-    hb_set_add (closure, subr_num);
+    closure->add (subr_num);
     collect_subr_refs_in_str (subrs[subr_num], param);
   }
 
diff --git a/src/hb-subset-cff1.cc b/src/hb-subset-cff1.cc
index 21bd97f..e9e0757 100644
--- a/src/hb-subset-cff1.cc
+++ b/src/hb-subset-cff1.cc
@@ -389,7 +389,7 @@
     byte_str_ref_t    str_ref = env.str_ref;
     env.call_subr (subrs, type);
     param.current_parsed_str->add_call_op (op, str_ref, env.context.subr_num);
-    hb_set_add (closure, env.context.subr_num);
+    closure->add (env.context.subr_num);
     param.set_current_str (env, true);
   }
 
diff --git a/src/hb-subset-cff2.cc b/src/hb-subset-cff2.cc
index 9bdd0ee..7edc3f5 100644
--- a/src/hb-subset-cff2.cc
+++ b/src/hb-subset-cff2.cc
@@ -219,7 +219,7 @@
     byte_str_ref_t    str_ref = env.str_ref;
     env.call_subr (subrs, type);
     param.current_parsed_str->add_call_op (op, str_ref, env.context.subr_num);
-    hb_set_add (closure, env.context.subr_num);
+    closure->add (env.context.subr_num);
     param.set_current_str (env, true);
   }
 
diff --git a/src/hb-subset-plan.cc b/src/hb-subset-plan.cc
index 9a52c55..147d7f0 100644
--- a/src/hb-subset-plan.cc
+++ b/src/hb-subset-plan.cc
@@ -43,7 +43,7 @@
     // Already visited this gid, ignore.
     return;
 
-  hb_set_add (gids_to_retain, gid);
+  gids_to_retain->add (gid);
 
   hb_bytes_t glyph_bytes = glyf.bytes_for_glyph (gid);
   const OT::glyf::GlyphHeader &glyph_header = *glyph_bytes.as<OT::glyf::GlyphHeader> ();
@@ -54,14 +54,14 @@
 #ifndef HB_NO_SUBSET_CFF
 static inline void
 _add_cff_seac_components (const OT::cff1::accelerator_t &cff,
-	   hb_codepoint_t gid,
-	   hb_set_t *gids_to_retain)
+			  hb_codepoint_t gid,
+			  hb_set_t *gids_to_retain)
 {
   hb_codepoint_t base_gid, accent_gid;
   if (cff.get_seac_components (gid, &base_gid, &accent_gid))
   {
-    hb_set_add (gids_to_retain, base_gid);
-    hb_set_add (gids_to_retain, accent_gid);
+    gids_to_retain->add (base_gid);
+    gids_to_retain->add (accent_gid);
   }
 }
 #endif