Add test for BC_VARG slot revival

Author: corsix

test/trace/gc64_slot_revival.lua

@@ -5,3 +5,14 @@ do --- BC_KNIL
     f(nil, nil)
   end
 end
+
+do --- BC_VARG
+  local function f() end
+  local function g(...)
+    f()
+    f(...)
+  end
+  for i = 1,100 do
+    g()
+  end
+end