Draw borders without NCurses border for reducing API dependency
FFI::NCurses out, Curses in
Let move_cursor return the row number

because stdlib Curses::Window#refresh returns nil unlike that of ffi-ncurses, and thus the return value of move_cursor always be nil
stdlib Curses.refresh doesn't bring us the previous screen back
undef mvwaddstr
undef subwin
undef wclrtoeol
No more using ffi!