hurd: Add expected abilist files for x86_64

These were created by creating stub files, running 'make update-abi',
and reviewing the results.

Also, set baseline ABI to GLIBC_2.38, the (upcoming) first glibc
release to first have x86_64-gnu support.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>