Undo commit 2689d07c8dbe9ca50e76a10076a2c203d977bc0b

[b0rnh4ck]

Commit 2689d07c8dbe9ca50e76a10076a2c203d977bc0b should be reverted. "RtlCreateUserThread" is (obviously) not a syscall and, even if it was, the prototype is incorrect for x64 usage.