[Bug go/67198] [5/6 Regression] change of type of syscall.RawSockaddr.Data on ppc64 breaks compilation of existing programs

[boger at us dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67198

--- Comment #2 from boger at us dot ibm.com ---
I was asked to make this fix to gccgo.  A corresponding Docker fix is needed
which is described here https://github.com/docker/libcontainer/pull/625.

It is unfortunate it introduces an incompatibility which means that new Docker
source can't be built with older gccgo compilers, but this is a bug and could
lead to incorrect execution.  It is assuming the field is signed when it should
be treated as unsigned.