fix#773
* buffer_cat is renamed to buffers_cat
* buffer_cat_view is renamed to buffers_cat_view
Actions Required:
* Use buffers_cat instead of buffer_cat
* Use buffers_cat_view instead of buffer_cat_view
* This presence of the user-declared copy constructor makes
the compiler-provided copy assignment operator deprecated.
This change allows the compiler to provide both copy members
without deprecated behavior.
