Use Errno::OVERFLOW for y2038 errors.

On platforms where the underlying OS APIs are not y2038-ready, use
`OVERFLOW` rather than `INVALID` if a y2038 time value is provided,
to indicate that the time cannot be converted into a value that can
be passed to the OS.

This fixes tests/fs/y2038.rs and tests/time/y2038.re on 32-bit Linux
systems which lack `statx`, and is consistent with what libc
implementations do.

Author: sunfishcode

src/imp/linux_raw/fs/syscalls.rs

@@ -1269,7 +1269,7 @@ unsafe fn _utimensat_old(
                 .last_access
                 .tv_sec
                 .try_into()
-                .map_err(|_| io::Errno::INVAL)?,
+                .map_err(|_| io::Errno::OVERFLOW)?,
             tv_nsec: times
                 .last_access
                 .tv_nsec
@@ -1281,7 +1281,7 @@ unsafe fn _utimensat_old(
                 .last_modification
                 .tv_sec
                 .try_into()
-                .map_err(|_| io::Errno::INVAL)?,
+                .map_err(|_| io::Errno::OVERFLOW)?,
             tv_nsec: times
                 .last_modification
                 .tv_nsec

src/imp/linux_raw/time/syscalls.rs

@@ -129,7 +129,7 @@ unsafe fn timerfd_settime_old(
                 .it_interval
                 .tv_sec
                 .try_into()
-                .map_err(|_| io::Errno::INVAL)?,
+                .map_err(|_| io::Errno::OVERFLOW)?,
             tv_nsec: new_value
                 .it_interval
                 .tv_nsec
@@ -141,7 +141,7 @@ unsafe fn timerfd_settime_old(
                 .it_value
                 .tv_sec
                 .try_into()
-                .map_err(|_| io::Errno::INVAL)?,
+                .map_err(|_| io::Errno::OVERFLOW)?,
             tv_nsec: new_value
                 .it_value
                 .tv_nsec