Now that we've switched over to using the vDSO on CloudABI, it becomes a
lot easier for us to phase out old features. System call numbering is no
longer something that's part of the ABI. It's fully based on names. As
long as the numbering used by the kernel and the vDSO is consistent
(which it always is), it's all right.
Let's put this to the test by removing a system call (thread_tcb_set())
that's already unused for quite some time now, but was only left intact
to serve as a placeholder. Sync in the new system call table that uses
alphabetic sorting of system calls.
Obtained from: https://github.com/NuxiNL/cloudabi
