x/sys/unix: Seteuid/Setegid for linux

[gopherbot]

by dustin@criticalstack.com:

Missing syscall.Seteuid/Setegid for linux_amd64 and linux_386 syscall packages.

[minux]

Comment 1:

see also issue #1435.

[tklauser]

The syscall package is locked down, but the functions may be added to the x/sys/unix package.

[kawasin73]

There is unix.Setreuid() which can be the alternative for syscall.Seteuid(). However it does not call setreuid(2) for all threads in the process but only for the caller thread.