new option use_packing_layout

src/option.cpp

@@ -41,6 +41,8 @@ Option::Option()
     use_int8_storage = true;
     use_int8_arithmetic = false;
 
+    use_packing_layout = false;
+
     // sanitize
     if (num_threads <= 0)
         num_threads = 1;

src/option.h

@@ -84,6 +84,9 @@ public:
     bool use_fp16_arithmetic;
     bool use_int8_storage;
     bool use_int8_arithmetic;
+
+    //
+    bool use_packing_layout;
 };
 
 } // namespace ncnn