Linux: Add epoll_pwait2 (BZ #27359)

It is similar to epoll_wait, with the difference the timeout has
nanosecond resoluting by using struct timespec instead of int.

Although Linux interface only provides 64 bit time_t support, old
32 bit interface is also provided (so keep in sync with current
practice and to no force opt-in on 64 bit time_t).

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

sysdeps/unix/sysv/linux/Versions

@@ -293,6 +293,12 @@ libc {
 %endif
     close_range;
   }
+  GLIBC_2.35 {
+%ifdef TIME64_NON_DEFAULT
+    __epoll_pwait2_time64;
+%endif
+    epoll_pwait2;
+  }
   GLIBC_PRIVATE {
     # functions used in other libraries
     __syscall_rt_sigqueueinfo;