bits/syscall.h: add epoll_pwait2 from linux v5.11

see

  linux commit b0a0c2615f6f199a656ed8549d7dce625d77aa77
  epoll: wire up syscall epoll_pwait2

  linux commit 58169a52ebc9a733aeb5bea857bc5daa71a301bb
  epoll: add syscall epoll_pwait2

epoll_wait with struct timespec timeout instead of int. no time32 variant.
16 files changed