[Bug go/69966] New: libgo: Port syscall.SetsockoptUcred from golang

[doko at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69966

            Bug ID: 69966
           Summary: libgo: Port syscall.SetsockoptUcred from golang
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: go
          Assignee: ian at airs dot com
          Reporter: doko at gcc dot gnu.org
                CC: cmang at google dot com
  Target Milestone: ---

Created attachment 37796
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37796&action=edit
patch

Michael Vogt noticed a missing syscall in gccgo, which is available in golang.
Backport is attached.