Merge branch 'pm/build-persistent-https-with-recent-go' into maint

The build procedure for "git persistent-https" helper (in contrib/) has been updated so that it can be built with more recent versions of Go. * pm/build-persistent-https-with-recent-go: contrib/persistent-https: use Git version for build label contrib/persistent-https: update ldflags syntax for Go 1.7+