specify allocating array size for Hash#values

src/hash.c

@@ -1037,7 +1037,7 @@ mrb_hash_values(mrb_state *mrb, mrb_value hash)
 {
   khash_t(ht) *h = RHASH_TBL(hash);
   khiter_t k;
-  mrb_value ary = mrb_ary_new(mrb);
+  mrb_value ary = mrb_ary_new_capa(mrb, kh_size(h));
 
   if (!h) return ary;
   for (k = kh_begin(h); k != kh_end(h); k++) {

test/t/hash.rb

@@ -222,5 +222,6 @@ end
 assert('Hash#values', '15.2.13.4.28') do
   a = { 'abc_key' => 'abc_value' }
 
+  p a.values
   a.values == ['abc_value']
 end