[exemple_05.c] add missing header.
[exemple_05.c] display size_t with %u.
[exemple_06.c] add missing header.
[exemple_05.c] display size_t with %zu.
[exemple_07.c] add missing header.
[exemple_08.c] add missing header.
[exemple_06.c] check return value of copy_to/from_user.
[exemple_20.c] cast virtual/phys address to llx format.