Hi guix,

The github.com/golang/protobuf module contains several packages.
Only proto is currently packaged.  This change updates the module from
1.3.1 to 1.5.2 and packages the entire module.

This is needed as I am preparing to package lxd (github.com/lxc/lxd), 
which depends on the unpackaged packages from golang/protobuf.

This change replaces go-github-com-golang-protobuf-proto with 
go-github-com-golang-protobuf.

There are currently two packages that depend on 
go-github-com-golang-protobuf-proto.  I have tested this changeset by 
building both of these packages.

go-github-com-lucas-clemente-quic-go: this is a source only package that 
no other package uses.

syncthing: depends on go-github-com-golang-protobuf-proto via several 
intermediary packages.  After building, I've run some of the syncthing
executables and they appear to work.