Update golang.org/x/sys to 8dbc5d05d6edcc104950cc299a1ce6641235bc86 in
order to get the Major, Minor and Mkdev functions for every unix-like
OS. Use them instead of the locally defined versions which currently use
the Linux specific device major/minor encoding.
This means that the device number should now be properly encoded on e.g.
Darwin, FreeBSD or Solaris.
Also, the SIGUNUSED constant was removed from golang.org/x/sys/unix in
https://go-review.googlesource.com/61771 as it is also removed from the
respective glibc headers.
Remove it from signal.SignalMap as well after the golang.org/x/sys
re-vendoring.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
