Silences the following:
* Error due to no definition for `mode_t` in `liburing.h`
* Warning due to use of non-portable `#include <sys/poll.h>` and `#include <sys/signal.h>`
* Warning due to incorrect `printf` format specifier in `test/io_uring_register.c`
* Error due to missing declaration for `strcpy` in `test/sendmsg_fs_cve.c`
* Error due to missing declaration for `strerror` in `test/shutdown.c`
Signed-off-by: Mahdi Rakhshandehroo <mahdi.rakhshandehroo@gmail.com>